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Hoo Sze Yen
Form 4 Experiments
Physics SPM 2008
CHAPTER 1: INTRODUCTION TO PHYSICS 1.1 PENDULUM Hypothesis: The longer the length of a simple pendulum, the longer the period of oscillation. Aim of the experiment: To investigate how the period of a simple pendulum varies with its length. Variables: Manipulated: The length of the pendulum, l Responding: The period of the pendulum, T Constant: The mass of the pendulum bob, gravitational acceleration Apparatus/Materials: Pendulum bob, length of thread about 100 cm long, retort stand, stopwatch Setup:
Thread Length, l Retort stand
Pendulum
Procedure: 1. The thread is tied to the pendulum bob. The other end of the thread is tied around the arm of the retort stand so that it can swing freely. The length of the pendulum, l is measured to 80 cm as per the diagram. Chapter 1: Introduction to Physics
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2. With the thread taut and the bob at rest, the bob is lifted at a small amplitude (of not more than 10°). Ensure that the pendulum swings in a single plane. 3. The time for ten complete oscillations of the pendulum is measured using the stopwatch. 4. Step 3 is repeated, and the average of both readings are calculated. 5. The period of oscillation, T is calculated using the average reading divided by the number of oscillations, i.e. 10. 6. T2 is calculated by squaring the value of T. 7. Steps 1 to 6 are repeated using l = 70 cm, 60 cm, 50 cm, and 40 cm. 8. A graph T2 versus l is plotted. Recording of data: Length of pendulum, l (cm) 80 70 60 50 40
t1
Time of oscillations, t (s) t2 Average
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 vs l T2
Length of pendulum, l
Discussion: The graph of T2 versus l shows a straight line ing through the origin. This means that the period of oscillation increases with the length of the pendulum, with T2 directly proportional to l. Conclusion: The longer the length of the pendulum, the longer the period of oscillation. The hypothesis is proven valid.
Chapter 1: Introduction to Physics
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CHAPTER 2: FORCES AND MOTION 2.1 INCLINED PLANES Hypothesis: The larger the angle of incline, the higher the velocity just before reaching the end of the runway Aim of the experiment: To study the relationship between the velocity of motion and the angle of inclination Variables: Manipulated: Angle of incline Responding: Velocity just before reaching the end of the runway Constant: Length of runway Apparatus/Materials: Trolley, protractor, wooden blocks, cellophane tape, tickertimer, ticker tape, power supply, friction-compensated runway Setup:
Procedure: 1. The apparatus is set up as per the diagram, and the inclined angle of the plane is measured using a protractor. An initial angle of 5° is used. 2. The ticker-timer is started up and at the same time the trolley is released to slide down the plane. 3. The final velocity when the trolley reaches the end of the plane is calculated using the distance of 10 ticks on the ticker tape. 4. The procedure is repeated by changing the angle of incline to 10°, 15°, 20° and 25°.
Chapter 2: Forces and Motion
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Results: Angle of incline (˚) Final velocity (m s-1) 5 10 15 20 25 Analysis: A graph of the velocity of the trolley against the angle of incline is plotted as follows: Velocity (m s-1)
Angle of incline (°) Conclusion: A higher angle of incline will have a higher velocity at the end of the runway. Hypothesis accepted. Note: The experiment can be modified by making the angle constant and varying the height and length of the runway. Changes must be made accordingly: hypothesis, variable list, procedure, table, analysis, conclusion.
Chapter 2: Forces and Motion
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2.2 INERTIA Option 1: Using a saw blade Hypothesis: The larger the mass, the larger the inertia Aim of the experiment: To study the effect of mass on the inertia of an object Variables: Manipulated: Mass, m Responding: Period of oscillation, T Constant: Stiffness of blade, distance of the centre of the plasticine from the clamp Apparatus/Materials: Jigsaw blade, G-clamp, stopwatch, and plasticine spheres of mass 20 g, 40 g, 60 g, 80 g, and 100 g Setup:
Procedure: 1. One end of the jigsaw blade is clamped to the leg of a table with a G-clamp as per the diagram drawn. 2. A 20 g plasticine ball is fixed at the free end of the blade. 3. The free end of the blade is displaced horizontally and released so that it oscillates. The time for 10 complete oscillations is measured using a stopwatch. This step is repeated. The average of 10 oscillations is calculated. Then, the period of oscillation is determined. 4. Steps 2 and 3 are repeated using plasticine balls with masses 40 g, 60 g, 80 g, and 100 g. 5. A graph of T2 versus mass of load, m is drawn.
Chapter 2: Forces and Motion
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Results: Mass of load, m (g) 20 40 60 80 100
Form 4 Experiments
Time of oscillations, t (s) t1 t2 Average
Physics SPM 2008
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line ing through the origin. This means that the period of oscillation increases with the mass of the load; that is, an object with a large mass has a large inertia. Conclusion: Objects with a large mass have a large inertia. This is the reason why it is difficult to set an object of large mass in motion or to stop it. The hypothesis is valid.
Option 2: Using an inertia balance Hypothesis: The larger the mass, the bigger the inertia Aim of the experiment: To study the effect of mass on the inertia of an object Variables: Manipulated: Mass, m Responding: Period of oscillation, T Constant: Stiffness of the inertia balance Apparatus/Materials: Inertia balance, masses for the inertia balance, G-clamp, stopwatch
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. The inertia balance is set up by clamping it onto one end of the table as shown in the figure above. 2. One mass is placed into the inertia balance. The inertia balance is displaced to one side so that it oscillates in a horizontal plane. 3. The time for 10 complete oscillations is measured using a stopwatch. This step is repeated. The average of 10 oscillations is calculated. Then, the period of oscillation is determined. 4. Steps 2 and 3 are repeated using two and three masses on the inertia balance. 5. A graph of T2 versus number of masses, n is drawn. Results: Number of masses, n 1 2 3
t1
Time of oscillations, t (s) t2 Average
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line ing through the origin. This means that the period of oscillation increases with the mass of the load; that is, an object with a large mass has a large inertia. Conclusion: Objects with a large mass have a large inertia. This is the reason why it is difficult to set an object of large mass in motion or to stop it. The hypothesis is valid. Chapter 2: Forces and Motion
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2.3 PRINCIPLE OF CONSERVATION OF MOMENTUM Experiment 1: Elastic collisions Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys colliding with each other elastically Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface of ramp used Apparatus/Materials: Friction-compensated runway, ticker-timer, A.C. power supply, trolleys, wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The runway is adjusted so that it is friction-compensated. 3. Two trolleys of equal mass are selected. A spring-loaded piston is fixed to the front end of trolley A. 4. Two pieces of ticker tape are attached to trolleys A and B respectively with cellophane tape. The ticker tapes are separately ed through the same ticker-timer. 5. The ticker-timer is switched on and trolley A is given a slight push so that it moves down the runway at uniform velocity and collides with trolley B which is stationary. 6. The ticker-timer is switched off when both trolleys reach the end of the runway. 7. From the ticker tapes of trolleys A and B, the final velocities are determined. 8. Momentum is calculated using the formula p = mv. 9. The experiment is repeated using different masses of trolleys.
Chapter 2: Forces and Motion
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Recording of data: mA mB Before collision uA Initial total momentum, mAuA m m 2m m 2m m 2m 2m
vA
Physics SPM 2008
vB
After collision Final total momentum, mAvA + mBvB
Analysis: From the above table, it is found that: Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Experiment 2: Inelastic collisions Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys colliding with each other inelastically Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface of ramp used Apparatus/Materials: Friction-compensated runway, ticker-timer, A.C. power supply, trolleys, wooden block, ticker tape, cellophane tape, plasticine / Velcro Setup:
Chapter 2: Forces and Motion
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Procedure: 1. The apparatus is set up as shown in the diagram. 2. The runway is adjusted so that it is friction-compensated. 3. Two trolleys of equal mass are selected. Plasticine is fixed to the front end of trolley A. (Alternatively, use Velcro pads) 4. A ticker tape is attached to trolley A with cellophane tape. The ticker tape is ed through the ticker-timer. 5. The ticker-timer is switched on and trolley A is given a slight push so that it moves down the runway at uniform velocity and collides with trolley B which is stationary. 6. The ticker-timer is switched off when both trolleys reach the end of the runway. 7. The final velocity is determined from the ticker tape. 8. Momentum is calculated using the formula p = mv. 9. The experiment is repeated using different masses of trolleys. Results: mA mB u m m 2m 2m
Before collision Initial total momentum, mAuA
v
After collision Final total momentum, (mA + mB) v
m 2m m 2m
Analysis: From the above table, it is found that: Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Experiment 3: Explosion Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys moving away from each other from an initial stationary position Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface used
Chapter 2: Forces and Motion
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Apparatus/Materials: Trolleys, wooden blocks, ticker tape, cellophane tape Setup:
Before explosion
After explosion
Procedure: 1. The apparatus is set up as shown in the diagram. 2. Two trolleys A and B of equal mass are placed in with each other on an even and smooth surface. Two wooden blocks are placed on the same row at the end of each trolley respectively. 3. The vertical trigger on trolley B is given a light tap to release the spring-loaded piston which then pushes the trolleys apart. The trolleys collide with the wooden blocks. 4. The positions of the wooden blocks are adjusted so that both the trolleys collide with them at the same time. 5. The distances, dA and dB are measured and recorded. 6. The experiment is repeated with different masses of trolleys. Results: Before explosion Initial total momentum 0 0 0 0
After explosion Mass of trolley A, mA m m 2m 2m
Mass of trolley B, mB m 2m m 2m
Distance traveled by trolley A, dA
Distance traveled by trolley B, dB
Final total momentum, mAdA + mB(-dB)
Analysis: Because both trolleys hit the wooden blocks at the same time, the velocity of the trolleys can be represented by the distance traveled by the trolleys. From the above table, it is found that: Initial total momentum = 0 Final total momentum = 0 ∴ Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Chapter 2: Forces and Motion
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2.4 FORCE, MASS AND ACCELERATION Experiment 1: Relationship between acceleration and mass when force is constant Hypothesis: When the force applied is constant, the acceleration of an object decreases when its mass increases Aim of the experiment: To study the effect of mass of an object on its acceleration if the applied force is constant Variables: Manipulated: Mass, m Responding: Acceleration, a Constant: Applied force, F Apparatus/Materials: Ticker-timer, A.C. power supply, trolleys, elastic band, runway, wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A ticker-tape is attached to the trolley and ed through the ticker-timer. 3. The ticker-timer is switched on and the trolley is pulled down the inclined runway with an elastic band attached to the hind post of the trolley. 4. The elastic band must be stretched to a fix length that is maintained throughout the motion down the runway. 5. When the trolley reaches the end of the runway, the ticker-timer is switched off and the ticker tape is removed. 6. Starting from a clearly printed dot, the ticker tape is divided into strips with each strip containing 10 ticks. 7. A ticker tape chart is constructed, and from the chart, the acceleration of the trolley is calculated. 8. The experiment is repeated using 2 and 3 trolleys. The elastic band must be stretched to the same fixed length as in step 4. Chapter 2: Forces and Motion
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Results: Mass of trolley, m (kg)
1 m
Physics SPM 2008
Acceleration, a (m s-2)
1 trolley 2 trolleys 3 trolleys Analysis: A graph of a against
1 is drawn. m
a
1 m From the graph, it shows that aα
1 m
Conclusion: The acceleration of an object decreases when the mass increases. Hypothesis proven.
Experiment 2: Relationship between acceleration and force when mass is constant Hypothesis: When the mass is constant, the acceleration of an object increases when the applied force increases Aim of the experiment: To study the effect of force on an object’s acceleration if its mass is constant Variables: Manipulated: Applied force, F Responding: Acceleration, a Constant: Mass, m Apparatus/Materials: Ticker-timer, A.C. power supply, trolleys, elastic band, runway, wooden block, ticker tape, cellophane tape
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A ticker-tape is attached to the trolley and ed through the ticker-timer. 3. The ticker-timer is switched on and the trolley is pulled down the inclined runway with an elastic band attached to the hind post of the trolley. 4. The elastic band must be stretched to a fix length that is maintained throughout the motion down the runway. 5. When the trolley reaches the end of the runway, the ticker-timer is switched off and the ticker tape is removed. 6. Starting from a clearly printed dot, the ticker tape is divided into strips with each strip containing 10 ticks. 7. A ticker tape chart is constructed, and from the chart, the acceleration of the trolley is calculated. 8. The experiment is repeated using 2 and 3 elastic bands. The elastic bands must be stretched to the same fixed length as in step 4. Results: Force applied, F 1 unit 2 units 3 units
Acceleration, a (m s-2)
Analysis: A graph of a against F is drawn. a
F From the graph, it shows that a α F Conclusion: The acceleration of an object increases when the applied force increases. Hypothesis proven.
Chapter 2: Forces and Motion
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2.5 GRAVITATIONAL ACCELERATION Hypothesis: Gravitational acceleration does not depend on an object’s mass Aim of the experiment: To measure the acceleration due to gravity Variables: Manipulated: Mass, m Responding: Gravitational acceleration, g Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply, retort stand, weights (50 g – 250 g), G-clamp, cellophane tape, soft board Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above. 2. One end of the ticker tape is attached to a 50 g weight with cellophane tape, and the other end is ed through the ticker timer. 3. The ticker-timer is switched on and the weight is released so that it falls onto the soft board. 4. The ticker-timer is switched off when the weight lands on the soft board. 5. Gravitational acceleration is calculated from the middle portion of the ticker tape. 6. The experiment is repeated with weights of mass 100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Results: Mass of weights (g) 50 100 150 200 250
Free fall acceleration (m s-2)
Analysis: From the table above, it is found that the gravitational acceleration for all the weights of different masses are the same. Discussion: • The value of the gravitational acceleration, g obtained is less than the standard value of 9.81 m s-2 • This is because the weight is not falling freely. It is affected by: o Air resistance o Friction between ticker tape and ticker-timer Conclusion Gravitational acceleration is not dependent on the mass of the object. Hypothesis proven.
2.6 PRINCIPLE OF CONSERVATION OF ENERGY Hypothesis: Energy cannot be created or destroyed, it can only change form. Aim of the experiment: To investigate the conversion of gravitational potential energy to kinetic energy. Variables: Manipulated: Mass, m Responding: Final velocity, v Constant: Height, h Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply, trolley, thread, weights, smooth pulley, friction-compensated runway, soft board, cellophane tape
Chapter 2: Forces and Motion
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Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above. 2. One end of the ticker tape is attached to the back of the trolley with cellophane tape and the other end is ed through the ticker-timer. 3. The ticker-timer is switched on, and the trolley is released. 4. The final velocity of the trolley and the weight is determined from the ticker tape obtained. 5. The experiment is repeated with different masses of trolleys and weights. Results: Mass of trolley = M kg Mass of weight = m kg Height of weight before release = h m Final velocity of trolley and weight = v m s-1 Loss of potential energy of the weight = mgh Final kinetic energy of the trolley and the weight = ½ (M + m) v2 It is found that ½ (M + m) v2 = mgh Conclusion The loss of potential energy is converted to kinetic energy. Hypothesis proven. Note: The experiment can be modified by making the mass constant and changing the height of the weight’s release. Changes must be made to the variables list and to the last step of the procedure.
Chapter 2: Forces and Motion
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2.7 HOOKE’S LAW Hypothesis: The bigger the weight, the longer the spring extension Aim of the experiment: To determine the relationship between the weight and the spring extension Variables: Manipulated: Weight of the load Responding: Spring extension Constant: Spring constant Apparatus and Materials: Spring, pin, weights, plasticine, retort stand, metre rule Setup:
Procedure: 1. The apparatus is setup as shown in the diagram. 2. The length of the spring without any weights, l0 is measured using the metre rule with the pin as reference. 3. A 50 g weight is hung from the bottom of the spring. The new length of the spring, l is measured. The spring extension is l – l0. 4. Step 4 is repeated with weights 100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Results: Original length of spring = l0 = __________ cm Load mass (g) 50 g 100 g 150 g 200 g 250 g
Load weight (N) 0.5 N 1.0 N 1.5 N 2.0 N 2.5 N
Spring length, l (cm)
Spring extension, x = l – l0 (cm)
Analysis: A graph of spring extension, x against weight, F is plotted. x
F The x-F graph is a linear graph which es through the origin. This shows that the extension of the spring is directly proportional to the stretching force. Conclusion: Hypothesis proven.
Chapter 2: Forces and Motion
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CHAPTER 3: FORCES AND PRESSURE 3.1 PRESSURE IN LIQUIDS Experiment 1: Water pressure and depth Hypothesis: Water pressure increases with depth Aim of the experiment: To find the relationship between the pressure in a liquid according to its depth Variables: Manipulated: Depth of liquid Responding: Pressure in liquid Constant: Density of liquid Apparatus and Materials: Measuring cylinder, thistle funnel, rubber tube, manometer, metre rule Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. The measuring cylinder is completely filled with water. 3. The thistle funnel is lowered into the water to a depth of 10.0 cm. The manometer reading is measured. The difference in the liquid heights in the manometer represent the pressure reading. 4. Step 3 is repeated with values of depth 20.0 cm, 30.0 cm, 40.0 cm and 50.0 cm.
Chapter 3: Forces and Pressure
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Results: Depth (cm) Manometer reading (cm) 10.0 20.0 30.0 40.0 50.0
Analysis: A graph of pressure against depth is drawn. Pressure
Depth Conclusion: It is observed that the manometer reading increases as the depth of the thistle funnel increases. This shows that the pressure increases with the depth of the liquid. Hypothesis proven.
Experiment 2: Water pressure and density Hypothesis: Pressure in liquid increases with its density Aim of the experiment: To find the relationship between the pressure in a liquid and its density Variables: Manipulated: Density of liquid Responding: Pressure in liquid Constant: Depth of liquid Apparatus and Materials: Measuring cylinder, thistle funnel, rubber tube, manometer, metre rule, water, glycerin, alcohol
Chapter 3: Forces and Pressure
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Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. The measuring cylinder is completely filled with water. 3. The thistle funnel is lowered into the water to a depth of 50.0 cm. The manometer reading is measured. The difference in the liquid heights in the manometer represent the pressure reading. 4. The experiment is repeated by replacing the water with glycerin (density = 1300 kg m-3) and alcohol (density = 800 kg m-3). Results: Depth within liquid = 50.0 cm Liquid Density (kg m-3) Manometer reading (cm) Water 1000 Glycerin 1300 Alcohol 800
Conclusion: It is observed that the manometer reading increases as the density of the liquid increases. This shows that the pressure increases with the density of the liquid. Hypothesis proven.
Chapter 3: Forces and Pressure
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3.2 ARCHIMEDES’ PRINCIPLE Hypothesis: The buoyant force on an object in a liquid is equal to the weight of the liquid displaced Aim of the experiment: To find the relationship between the buoyant force acting upon an object in a liquid and the weight of the liquid displaced Variables: Manipulated: Weight of the object Responding: Buoyant force / Weight of liquid displaced Constant: Density of liquid used Apparatus and Materials: Eureka tin, spring balance, stone, thread, beaker, triple beam balance Setup:
Procedure: 1. A beaker is weighed with the triple beam balance and its mass, m1 is recorded. 2. The Eureka tin is filled with water right up to the level of the overflow hole. The beaker is placed beneath the spout to catch any water that flows out. 3. A stone is suspended from the spring balance with thread and its weight in air, W1 is read from the spring balance.
Chapter 3: Forces and Pressure
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4. The stone is lowered into the Eureka tin until it is completely immersed in water without touching the bottom of the Eureka tin. The water will overflow into the beaker. 5. The spring balance reading, W2 is recorded. 6. The beaker with water is weighed with the triple beam balance, and the mass, m2 is recorded. Results: Weight of stone in air = W1 Weight of stone in water = W2 Buoyant force acting on the stone = W2 – W1 Weight of the empty beaker = m1g Weight of the beaker and displaced water = m2g Weight of the displaced water = (m2 – m1)g It is found that W2 – W1 = (m2 – m1)g Discussion: The loss of weight of the stone immersed in water is due to the buoyant force of the water acting upon it. From the results, it is found that the loss in weight of the stone is equal to the weight of water displaced. Conclusion: Buoyant force on the stone = Weight of the water displaced by the stone Hypothesis proven. Note: Experiment can be modified to compare the weight of different sized stones and the values of buoyant force
3.3 PASCAL’S PRINCIPLE Hypothesis: The liquid pressure exerted on a small surface is equal to the liquid pressure exerted on a large surface in a closed system Aim of the experiment: To find the relationship between the pressure in a small syringe and a large syringe in a closed system Variables: Manipulated: Pressure acting on the small syringe Responding: Pressure acting on the large syringe Constant: Density of liquid within the system
Chapter 3: Forces and Pressure
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Apparatus and Materials: 5 ml syringe, 10 ml syringe, several weights, rubber tube, two retort stands Setup:
Procedure: 1. The diameters of the piston of both syringes are measured and their cross-sectional areas are calculated. 2. The two syringes are each mounted on a retort stand. 3. The syringes are filled with water and are securely connected to each other with a rubber tube as shown in the diagram. 4. A weight is placed on the piston of the small syringe. 5. Weights are added to the piston of the large syringe until the water levels in the two syringes are the same (i.e. syringes are in equilibrium). 6. The forces, F1 and F2 on the syringes are calculated. 7. The pressure, P1 and P2 exerted on the syringes are compared. Results: Syringe size
Cross-sectional area, A
Mass of the weight, m
Force exerted on the syringe, F = mg
Small Large
A1 A2
m1 m2
F1 F2
Pressure, P F = A P1 P2
Discussion: It is found that the pressure, P1 exerted on the piston of the small syringe is equal to the pressure, P2 exerted on the piston of the large syringe. Conclusion: The water pressure exerted on the piston of the small syringe is equal to the water pressure exerted on the piston of the large syringe. This shows that the pressure applied to the piston of the small syringe is transmitted to the piston of the large syringe. Hypothesis proven.
Chapter 3: Forces and Pressure
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3.4 BERNOULLI’S PRINCIPLE Hypothesis: When the velocity of water increases, its pressure decreases and vice versa. Aim of the experiment: To find the effects of movement on the pressure exerted by a fluid Variables: Manipulated: Velocity of the water Responding: Pressure of the water Constant: Density of the water Apparatus and Materials: Uniform glass tube, Venturi tube, rubber hose, water from a tap Procedure: 1. A uniform glass tube is connected to a tap with a rubber hose. The other end of the tube is closed up with a stopper. 2. The tap is opened slowly so that water flows into it. 3. The levels of the vertical tubes are observed. 4. The stopper is then removed. The tap is adjusted so that the water flows through the tube at a uniform rate. 5. The levels of the vertical tubes are observed. 6. The experiment is repeated by replacing the uniform glass tube with a Venturi tube. Results: Uniform glass tube:
With the stopper
Chapter 3: Forces and Pressure
Without the stopper
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Venturi tube:
With the stopper
Without the stopper
Discussion: • The height of the water in the vertical tube represents the pressure at that point. • When water is not flowing, the pressure along the entire tube is the same, therefore the water levels in all three vertical tubes are the same. • For the uniform glass tube: o Water flows from high pressure to low pressure. o Therefore, the water levels are decreasing because the pressure is decreasing. • For the Venturi tube: o The velocity at Y is higher because of the smaller cross-sectional area. o Therefore, the pressure at Y is the lowest. o Pressure still decreases from X to Z because water flows from high pressure to low pressure. Conclusion: The higher the water velocity, the lower the pressure at that point. Hypothesis proven.
Chapter 3: Forces and Pressure
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CHAPTER 4: HEAT AND ENERGY 4.1 SPECIFIC HEAT CAPACITY Experiment 1: Rise in temperature – varying mass, fixed amount of heat Hypothesis: The bigger the mass of water, the smaller the rise in temperature when supplied with the same amount of heat Aim of the experiment: To determine the rise in temperature of water with varying masses Variables: Manipulated: Mass of water, m Responding: Rise in temperature, θ Constant: Amount of heat supplied, Q Apparatus and Materials: Beaker, electric heater, thermometer, stopwatch, triple beam balance, stirrer, polystyrene sheet, felt cloth Set up:
Procedure: 1. With the help of a triple beam balance, fill a beaker with water of mass 0.40 kg. 2. The apparatus is set up as shown in the diagram. 3. The initial temperature of the water, θ1 is measured using a thermometer and is recorded. 4. The electric heater is placed into the water and is switched on for 1 minute. The water is continuously stirred. 5. The water is continuously stirred even after the heater has been switched off. The
Chapter 4: Heat and Energy
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6. The highest temperature the water reaches, θ2 is measured and recorded. The rise in temperature, θ = θ2 – θ1 is calculated. 7. The experiment is repeated with water of mass 0.50 kg, 0.60 kg, 0.70 kg, and 0.80 kg. 1 8. A graph of θ against m and a graph of θ against are plotted. m Results: Mass of water, Initial Final Rise in 1 (kg-1) m (kg) temperature, temperature, temperature, θ m θ1 (°C) θ2 (°C) = θ2 – θ1 (°C) 0.40 0.50 0.60 0.70 0.80
Analysis: • The amount of heat supplied is made constant by using the same heater for the same period of time. • The following graphs are obtained:
Conclusion: The rise in temperature is inversely proportional to the mass when a constant amount of heat is supplied. Hypothesis proven.
Experiment 2: Rise in temperature – fixed mass, varying amount of heat Hypothesis: When more heat is supplied to water of fixed mass, the rise in temperature is greater Aim of the experiment: To determine the rise in temperature of water with varying amounts of heat Variables: Manipulated: Amount of heat supplied, Q Responding: Rise in temperature, θ Constant: Mass of water, m
Chapter 4: Heat and Energy
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Apparatus and Materials: Beaker, electric heater, thermometer, stopwatch, triple beam balance, stirrer, polystyrene sheet, felt cloth Set up:
Procedure: 1. With the help of a triple beam balance, fill a beaker with water of mass 0.50 kg. 2. The apparatus is set up as shown in the diagram. 3. The initial temperature of the water, θ1 is measured using a thermometer and is recorded. 4. The electric heater is placed into the water and is switched on for 1 minute. The water is continuously stirred. 5. The water is continuously stirred even after the heater has been switched off. 6. The highest temperature the water reaches, θ2 is measured and recorded. The rise in temperature, θ = θ2 – θ1 is calculated. 7. The experiment is repeated with water of the same mass but with heating time of 2 minutes, 3 minutes, and 4 minutes. 8. A graph of θ against t is plotted. Results: Heating time (minute)
Initial temperature, θ1 (°C)
Final temperature, θ2 (°C)
Rise in temperature, θ = θ2 – θ1 (°C)
1 2 3 4 Analysis: • Because the same heater with fixed power is used, the heating time, t is defined operationally as the heat quantity. • The following graph is obtained:
Chapter 4: Heat and Energy
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Conclusion: When an object of fixed mass is heated, the rise in temperature changes proportionally to the amount of heat supplied. Hypothesis proven.
Experiment 3: Determining the specific heat capacity of aluminium Aim of the experiment: To determine the specific heat capacity of aluminium Apparatus and Materials: Aluminium cylinder, weighing scale, electric heater, thermometer, power supply, felt cloth, polystyrene sheet, stopwatch, lubricating oil Set up:
Procedure: 1. An aluminium cylinder with two cavities is weighed and its mass, m is recorded. 2. The electrical power of the heater, P is recorded. 3. The electrical heater is then placed inside the large cavity in the centre of the cylinder. 4. The thermometer is then placed in the small cavity of the aluminium cylinder. 5. A few drops of lubricating oil are added to both cavities to ensure good thermal (better heat transfer). 6. The apparatus is set up as shown in the diagram above. 7. The initial temperature of the aluminium cylinder, θ1 is recorded. 8. The electric heater is switched on and the stopwatch is started simultaneously. 9. After heating for t seconds, the heater is switched off. The highest reading on the thermometer, θ2 is recorded. 10. The experiment is repeated and an average value of c is calculated.
Chapter 4: Heat and Energy
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Results: Electric power of heater = P Watt Heating time = t seconds Mass of aluminium cylinder = m kg Initial temperature of the aluminium cylinder = θ1 Final temperature of the aluminium cylinder = θ2 Temperature rise = θ2 – θ1 Electrical energy supplied by the heater = Pt Heat energy absorbed by the aluminium cylinder = mcθ On the assumption that there is no heat loss to the surroundings: Heat supplied = Heat absorbed Pt = mcθ Pt Specific heat capacity, c = mθ Discussion: • The aluminium cylinder is wrapped with a felt cloth to reduce the heat loss to the surroundings and the polystyrene sheet acts as a heat insulator to avoid heat loss to the surface of the table. • The value of the specific heat capacity of aluminium, c determined in the experiment is larger than the standard value. This is because there will be some heat lost to the surrounding. • The temperature of the aluminium cylinder will continue to rise after the electrical heater has been switched off because there is still some heat transfer from the heater to the cylinder. Conclusion: The specific heat capacity of aluminium is a constant.
4.2 SPECIFIC LATENT HEAT Experiment 1: Heating of naphthalene Hypothesis: During the change of state of naphthalene from solid to liquid, there is no change in temperature when heat is continuously supplied Aim of the experiment: To observe the change in temperature when naphthalene is melting Apparatus and Materials: Boiling tube, naphthalene powder, beaker, thermometer, Bunsen burner, stopwatch, retort stand, tripod stand, wire gauze Chapter 4: Heat and Energy
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Set up:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The initial temperature of the naphthalene is recorded. 3. The Bunsen burner is lighted and the stopwatch started. 4. The temperature of the naphthalene is recorded at 1 minute intervals until the temperature reaches 100°C. 5. The state of the naphthalene is observed and tabulated throughout the heating process. 6. A graph of temperature against time is drawn. Results: Time, t (minute) Temperature of naphthalene, θ (°C) 0 1 2 3 …
Graph of temperature against time:
Discussion: • The temperature-time graph shows that the temperature of naphthalene rises until the naphthalene starts to melt. • The naphthalene starts to melt at 80°C. The temperature remains constant at this value for several minutes while the naphthalene continues to melt with the heat.
Chapter 4: Heat and Energy
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•
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After the naphthalene has completely melted, the temperature begins to rise with continued heating.
Conclusion: The temperature of the naphthalene remains constant during a change of state from solid to liquid.
Experiment 2: Cooling of naphthalene Hypothesis: During the change of state of naphthalene from liquid to solid, there is no change in temperature Aim of the experiment: To observe the change in temperature when naphthalene is freezing Apparatus and Materials: Boiling tube, naphthalene powder, beaker, thermometer, Bunsen burner, stopwatch, retort stand, tripod stand, wire gauze Set up:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The naphthalene is heated until the temperature reaches 95°C. 3. The boiling tube is then removed from the water bath and the outer part of the tube is dried. 4. The temperature of the naphthalene is recorded every minute until the temperature drops to about 60°C. 5. A graph of temperature against time is drawn.
Chapter 4: Heat and Energy
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Results: Time, t (minute) Temperature of naphthalene, θ (°C) 0 1 2 3 …
Graph of temperature against time:
Discussion: • The temperature-time graph shows that the temperature of naphthalene drops until 80°C where it stays constant for several minutes as it freezes. • After the naphthalene has completely frozen, the temperature continues to drop. Conclusion: The temperature of the naphthalene remains constant during a change of state from liquid to solid.
Experiment 3: Latent heat of fusion (ice) Aim of the experiment: To determine the latent heat of fusion of ice Apparatus and Materials: Pure ice, electric immersion heater, filter funnel, beaker, stopwatch, weighing balance, power supply, retort stand, clamp
Chapter 4: Heat and Energy
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Set up:
Set A
Set B
Procedure: 1. The mass of two empty beakers, A and B are determined using the weighing balance. 2. The apparatus is arranged as shown in the diagram above. 3. Each of the two filter funnels is filled with ice cubes. 4. The immersion heater in Set A, the control experiment, is not connected to the power supply. The purpose of Set A is to determine the mass of the ice melted by the surrounding heat. The heater in Set B is switched on. 5. When water starts to drip from the filter funnels at a steady rate, the stopwatch is started and the empty beakers A and B are placed beneath the filter funnels. 6. After a period of t seconds, the heater B is switched off. The masses of both beakers, A and B are determined using the weighing balance. 7. The experiment is repeated to get an average value. Results: Set A: Mass of empty beaker = mA1 kg Mass of beaker + water = mA2 kg Mass of ice melted by surrounding heat, ma = mA2 – mA1 kg Set B: Mass of empty beaker = mB1 kg Mass of beaker + water = mB2 kg Mass of ice melted by surrounding heat & immersion heater, mb = mB2 – mB1 kg Mass of ice melted by the electric immersion heater, m = mb – ma kg Electrical energy supplied by the electrical immersion heater, E = Pt Heat energy absorbed by the ice during melting, Q = mL Assuming there is no heat loss to the surroundings: Electrical energy supplied = Heat energy absorbed by the melting ice Pt = mL Pt Specific latent heat of fusion of ice, L = m Chapter 4: Heat and Energy
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Discussion: • The purpose of Set A, the control experiment, is to determine the mass of ice melted by the surrounding heat. • The immersion heater must be fully immersed in the ice cubes to avoid or reduce heat loss. • The stopwatch is not started simultaneously when the immersion heater is switched on because the immersion heater requires a time period before reaching a steady temperature. At this point, the rate of melting of ice will be steady. • The value of the specific latent heat of fusion of ice, L obtained in this experiment is higher than the standard value because part of the heat supplied by the heater is lost to the surroundings. Conclusion: The specific latent heat of fusion of ice is a constant.
Experiment 4: Latent heat of vapourisation (water) Aim of the experiment: To determine the latent heat of vapourisation of water Apparatus and Materials: Pure water, electric immersion heater, filter funnel, beaker, stopwatch, weighing balance, power supply, retort stand, clamp Set up:
Procedure: 1. The apparatus is set up as shown in the diagram above. 2. A beaker is placed on the platform of the electronic weighing balance. 3. The electric heater is fully immersed in the water and held in this position by being clamped to a retort stand. 4. The electric heater is switched on to heat the water to its boiling point. 5. When the water starts to boil at a steady rate, the stopwatch is started and the reading on the electronic balance, m1 is recorded. 6. The water is allowed to boil for a period of t seconds. 7. At the end of the period of t seconds, the reading on the electronic balance, m2 is recorded.
Chapter 4: Heat and Energy
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Results: Electrical power of heater = P Watt Time period of boiling = t seconds Electrical energy supplied by the electrical immersion heater, E = Pt Mass of water vapourised = m2 – m1 Heat energy absorbed by the water during vapourisation, Q = mL Assuming there is no heat loss to the surroundings: Electrical energy supplied = Heat energy absorbed by the vapourized water Pt = mL Pt Specific latent heat of vapourization of water, L = m Discussion: • The immersion heater must be fully immersed in the water to avoid or reduce heat loss. • The stopwatch is not started simultaneously when the immersion heater is switched on because the immersion heater requires a time period before reaching a steady temperature. At this point, the rate of heating of water will be steady. • The value of the specific latent heat of vapourization of water, L obtained in this experiment is higher than the standard value because part of the heat supplied by the heater is lost to the surroundings. Conclusion: The specific latent heat of vapourization of water is a constant.
4.3 BOYLE’S LAW Option 1: Changing the volume of air to measure pressure Hypothesis: When the volume of air decreases, the pressure increases when its mass and temperature is constant Aim: To investigate the relationship between the pressure and volume of air Variables: Manipulated: Volume of air within syringe Responding: Pressure of air Constant: Mass, temperature of air Apparatus and Materials: Rubber hose, Bordon gauge, 100 cm3 syringe Chapter 4: Heat and Energy
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Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The nose of the syringe is fitted with a rubber hose and the piston is adjusted so that air volume of 100 cm3 at atmospheric pressure is trapped in the syringe. 3. The rubber hose is connected to a Bourdon gauge and air pressure is read from the gauge. 4. The piston of the syringe is pushed in until the trapped air volume becomes 90 cm3 and the air pressure is read from the Bourdon gauge. 5. Step 4 is repeated for air volume values 80, 70, and 60 cm3. Results: Volume, V (cm3)
1 (cm-3) V
Pressure, P (Pa)
100 90 80 70 60 Analysis: • • •
1 is plotted. V A linear graph going through the origin is obtained. This indicates that pressure is inversely proportional to the volume of gas. A graph of P against
Conclusion: Gas pressure of fixed mass is inversely proportional to its volume.
Chapter 4: Heat and Energy
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Option 2: Changing the pressure of air to measure volume Hypothesis: When the pressure of air decreases, the volume increases when its mass and temperature is constant Aim: To investigate the relationship between the pressure and volume of air Variables: Manipulated: Pressure of air Responding: Volume of air trapped in the capillary tube Constant: Mass, temperature of air Apparatus and Materials: Bicycle pump, ruler, tank with oil, pressure gauge, glass tube Set up:
Procedure: 1. The apparatus is set up as shown in the diagram above. 2. The piston of the bicycle pump is pushed in to compress the air inside the glass tube until the pressure is 10 kPa. 3. When the reading on the pressure gauge is P, the volume of the air column, V is recorded. 4. Steps 1 and 2 are repeated for 5 pressure readings of 20 kPa, 30 kPa and 40 kPa.
Chapter 4: Heat and Energy
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Results: Pressure, P (kPa)
1 (Pa-1) P
Physics SPM 2008
Volume, V (cm3)
10 20 30 40 Analysis: • • •
1 is plotted. P A linear graph going through the origin is obtained. This indicates that pressure is inversely proportional to the volume of gas. A graph of V against
Conclusion: Volume of gas of fixed mass is inversely proportional to its pressure.
4.4 CHARLES’ LAW Hypothesis: When the temperature of air increases, the volume increases if the mass and pressure is constant Aim: To investigate the relationship between the volume and the temperature of gas Variables: Manipulated: Air temperature Responding: Air volume Constant: Mass and pressure of the trapped air Apparatus and Materials: Capillary tube, tall beaker, thermometer, Bunsen burner, tripod, wire gauze, retort stand, mercury or concentrated sulphuric acid, stirrer, ruler, ice, rubber band
Chapter 4: Heat and Energy
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Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The air to be studied is trapped in a capillary tube by concentrated sulphuric acid. 3. The capillary tube is fitted to a ruler using two rubber bands and the bottom end of the air column is ensured to match the zero marking on the ruler. 4. Water and ice is poured into the beaker until the whole air column is submerged. Water is then stirred until the temperature rises to 10 °C. The length of the air column and the temperature of the water are recorded. 5. Water is heated slowly while being stirred continuously. The length of the air column is recorded every 10 °C until the water temperature reaches 90 °C. Results: 10 20 30 40 50 60 70 80 90 Temperature, θ (°C) Length of air column, x (cm) Analysis: • A graph of x against θ is plotted. • A linear graph is obtained. • When extrapolated, length x = 0 occurs when gas temperature, θ = -273 °C
•
When the Celsius scale is replaced with the Kelvin scale, a linear graph that goes through origin is obtained.
Chapter 4: Heat and Energy
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Discussion: From the graph plotted, it is found that the length of the air column, x is directly proportional to its temperature, T (K). Because gas volume is directly proportional to the length of the column, it also indicates that gas volume is directly proportional to its absolute temperature. Conclusion: Gas volume of fixed mass is directly proportional to its absolute temperature
4.5 PRESSURE LAW Hypothesis: When the temperature of air increases, the pressure increases if the mass and volume is constant Aim: To investigate the relationship between the pressure and the temperature of gas Variables: Manipulated: Air temperature Responding: Air pressure Constant: Mass and volume of the trapped air Apparatus and Materials: Round-bottomed flask, mercury thermometer, Bourdon gauge, Bunsen burner, tripod, wire gauze, retort stand, stirrer, ice Set up:
Chapter 4: Heat and Energy
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Procedure: 1. Apparatus is set up as per the diagram. 2. The round-bottomed flask is submerged in water and the water bath with ice is stirred continuously until the temperature of the water bath is stable. 3. The temperature of the water is taken from the thermometer. 4. The reading from the Bourdon gauge is read at temperatures 30, 40, 50, 60, 70 and 80 °C. Results: Temperature, θ (°C) 30 40 50 60 70 80 Air pressure, P (Pa) Analysis: • A graph of P against θ is plotted. • A linear graph is obtained. • When extrapolated, pressure P = 0 occurs when gas temperature, θ = -273 °C
•
When the Celsius scale is replaced with the Kelvin scale, a linear graph that goes through origin is obtained.
Conclusion: Gas pressure of fixed mass is directly proportional to its absolute temperature
Chapter 4: Heat and Energy
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CHAPTER 5: LIGHT AND VISION 5.1 REFLECTION Hypothesis: The angle of reflection is equal to the angle of incidence Aim of the experiment: To study the relationship between the angle of incidence and angle of reflection Variables: Manipulated: Angle of incidence, i Responding: Angle of reflection, r Constant: Plane mirror used Apparatus/Materials: Light box, plane mirror, plasticine, paper, pencil, protractor Setup:
Procedure: 9. A straight line, PQ is drawn on a sheet of white paper. 10. The normal line, ON is drawn from a point at the centre of PQ. 11. With the aid of a protractor, lines at angles of incidence 15°, 30°, 45°, 60° and 75° to the normal line, are drawn to its left. 12. A plane mirror is erected along the line PQ. It is secured in this position with the aid of plasticine. 13. A ray of light from the ray box is directed along the 15° line. Two positions are marked with a pencil on the line of the reflected ray. 14. Step 5 is repeated for the other angles of incidence. 15. The plane mirror is removed. The reflected rays are drawn by ing the respective marks. 16. The angles of reflection corresponding with all the angle of incidence are measured. The results are tabulated.
Chapter 5: Light and Vision
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Results: Incident angle (˚) Reflected angle (˚) 15 30 45 60 75
Conclusion: The angle of incidence is equal to the angle of reflection.
5.2 CURVED MIRRORS Aim of the experiment: To study the characteristics of images formed by curved mirrors Apparatus/Materials: Concave mirror, convex mirror, plasticine, light bulb mounted on a wooden block, metre rule, white screen Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The focal length, f and the radius of curvature, r of the concave mirror, as supplied, are recorded. 3. The light bulb is positioned at a distance greater than the radius of curvature of the mirror, i.e. u > 2f. The white screen is moved between the concave mirror and the light bulb until an image is clearly focused on the screen. The image distance, v is measured by a metre rule and recorded. 4. Step 3 is repeated with the light bulb positioned at C (u = 2f), between C and F (f < u < 2f), at F (u = f), and between F and P (u < f).
Chapter 5: Light and Vision
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5. The values of u, v, and the characteristics of the images formed are recorded in a table. 6. The experiment is repeated by replacing the concave mirror with a convex mirror. Results: Concave mirror; Position of Object object distance, u (cm)
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual Inverted Magnified / Same size
Beyond C (u > 2f) At C (u = 2f) Between C and F (f < u < 2f) At F (u = f) Between F and P (u < 2f) Convex mirrors: For all positions, the image characteristics are: __________________________ Conclusion: • For concave mirrors, images formed can be real or virtual, whereas for convex mirrors, only virtual images are formed. • The characteristics of images formed by the concave mirror depend on the position of the object.
5.3 REFRACTION Hypothesis: The refracted light ray obeys Snell’s Law which states that the value of
sin i is a sin r
constant where i is the angle of incidence and r is the angle of refraction
Aim of the experiment: To study the relationship between the angle of incidence and angle of refraction
Chapter 5: Light and Vision
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Variables: Manipulated: Angle of incidence, i Responding: Angle of refraction, r Constant: Plane mirror used Apparatus/Materials: Ray box, glass block, paper, pencil Setup:
Procedure: 1. The outline of the glass block is traced on a sheet of white paper and labeled. 2. The glass block is removed. Point O is marked on one side of the glass block. With a protractor, lines forming angles of incidence 20°, 30°, 40°, 50° and 60° are drawn and marked. 3. The glass block is replaced on its outline on the paper. 4. A ray of light from the ray box is directed along 20° line. The ray emerging on the other side of the block is drawn. 5. Step 4 is repeated for the other angles of incidence. 6. The glass slab is removed. The points of incidence and the corresponding points of emergence are ed. The respective angles of refraction are measured with a protractor. sin i 7. The values of sin i, sin r, and are calculated. sin r Results: Angle of incidence, i (°) Angle of refraction, r (°) Sin i Sin r
n=
sin i sin r
20 30 40 50 60 Conclusion: It is found that
sin i is a constant. Hypothesis valid. sin r
Chapter 5: Light and Vision
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5.4 ACTUAL DEPTH & APPARENT DEPTH Hypothesis: The deeper the actual depth, the deeper the apparent depth Aim of the experiment: To study the relationship between the actual depth and apparent depth Variables: Manipulated: Actual depth, D Responding: Apparent depth, d Constant: Refractive index of medium (water), n Apparatus/Materials: Tall beaker, 2 pins, ruler, metre rule, retort stand Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A pin is mounted on a movable clamp on a retort stand. 3. Another pin is placed at the base of the tall beaker. Water is filled as the actual depth to D = 7.0 cm. 4. The object pin O is observed from the top, and pin I is adjusted vertically until it appears to meet pin O. At this point, the position of pin I matches the apparent depth, d of pin O. The apparent depth is measured from the top of the water level to the position of pin I. 5. Step 4 is repeated by changing the actual depth to 9.0 cm, 11.0 cm, 13.0 cm and 15.0 cm. 6. The results are tabulated and a graph of D against d is plotted.
Chapter 5: Light and Vision
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Results: Actual depth, D (cm) Apparent depth, d (cm) 7.0 9.0 11.0 13.0 15.0
Analysis: A linear graph that goes through origin is obtained. D
d Discussion: • The gradient of the graph is equal to the index of refraction of water. Conclusion: Hypothesis is valid
5.5 TOTAL INTERNAL REFLECTION Aim of the experiment: To determine the critical angle of glass Apparatus/Materials: Semicircular glass block, ray box, protractor, white paper, pencil Setup:
Procedure: 1. A semicircular glass block is placed on a sheet of white paper. The outline of the glass block is traced onto the paper with a sharp pencil. Chapter 5: Light and Vision
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2. The glass block is put aside. A normal line, NN’ is drawn through the centre point, O on the diameter. 3. The glass block is replaced on its outline. 4. A narrow beam of light from the ray box is directed at point O at a small angle of incidence. The refracted and reflected rays are observed. 5. The angle of incidence, i measured from the normal line is adjusted until the light ray is refracted along the length of the air-glass boundary. The point of entry of the light ray is marked and measured with a protractor. At this point, the incident angle is known as the critical angle, c. 6. The angle of incidence is increased and the resultant rays are observed. 7. The experiment is repeated by pointing the light ray through the other side of the semicircle. Results: • When i < c, part of the light ray is refracted to the air, and part of it will be reflected back within the glass block • When i = c, the light ray will be refracted along the length of the glass-air boundary • When i > c, no refraction occurs; all the light ray will be totally internally reflected within the glass block Analysis: The critical angle, c is a constant. 1 Refractive index of glass, n = sin c Conclusion: The refractive index of glass, n =
1 sin c
5.6 LENSES Hypothesis: The image produced by a convex lens is virtual or real depending on the position of the object. The characteristics of an image produced by a concave lens is not affected by the object distance. Variables: Manipulated: Object distance, u Responding: Image distance, v Constant: Focal length of lens, f Apparatus/Materials: Cardboard with a cross-wire in triangular cut-out, light bulb, lens holder, convex lens, concave lens, white screen
Chapter 5: Light and Vision
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Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The focal length, f of the convex lens supplied is recorded. 3. The object (triangle with a cross-wire) is placed at a distance greater than 2f from the convex lens. 4. The white screen is moved back and forth until a sharp image of the triangle is formed on the screen. The image distance, v is measured. The characteristics of the image are observed and recorded in a table. 5. Step 3 is repeated wit the object distances, u = 2f, f < u < 2f, u = f, and u < f. 6. For positions where the image cannot be formed on the screen, the screen is removed and the image is viewed through the lens from the other side of the lens. 7. The experiment is repeated by replacing the convex lens with a concave lens. Results: Convex lens: Position Object of object distance, u (cm)
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual Inverted Magnified / Same size
u > 2f u = 2f f < u < 2f u=f u < 2f Concave lens: For all positions, the image characteristics are: __________________________ Conclusion: • For convex lenses, images formed can be real or virtual, whereas for concave lenses, only virtual images are formed. • The characteristics of images formed by the convex lens depend on the position of the object.
Chapter 5: Light and Vision
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CHAPTER 1: INTRODUCTION TO PHYSICS 1.1 PENDULUM Hypothesis: The longer the length of a simple pendulum, the longer the period of oscillation. Aim of the experiment: To investigate how the period of a simple pendulum varies with its length. Variables: Manipulated: The length of the pendulum, l Responding: The period of the pendulum, T Constant: The mass of the pendulum bob, gravitational acceleration Apparatus/Materials: Pendulum bob, length of thread about 100 cm long, retort stand, stopwatch Setup:
Thread Length, l Retort stand
Pendulum
Procedure: 1. The thread is tied to the pendulum bob. The other end of the thread is tied around the arm of the retort stand so that it can swing freely. The length of the pendulum, l is measured to 80 cm as per the diagram. Chapter 1: Introduction to Physics
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2. With the thread taut and the bob at rest, the bob is lifted at a small amplitude (of not more than 10°). Ensure that the pendulum swings in a single plane. 3. The time for ten complete oscillations of the pendulum is measured using the stopwatch. 4. Step 3 is repeated, and the average of both readings are calculated. 5. The period of oscillation, T is calculated using the average reading divided by the number of oscillations, i.e. 10. 6. T2 is calculated by squaring the value of T. 7. Steps 1 to 6 are repeated using l = 70 cm, 60 cm, 50 cm, and 40 cm. 8. A graph T2 versus l is plotted. Recording of data: Length of pendulum, l (cm) 80 70 60 50 40
t1
Time of oscillations, t (s) t2 Average
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 vs l T2
Length of pendulum, l
Discussion: The graph of T2 versus l shows a straight line ing through the origin. This means that the period of oscillation increases with the length of the pendulum, with T2 directly proportional to l. Conclusion: The longer the length of the pendulum, the longer the period of oscillation. The hypothesis is proven valid.
Chapter 1: Introduction to Physics
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CHAPTER 2: FORCES AND MOTION 2.1 INCLINED PLANES Hypothesis: The larger the angle of incline, the higher the velocity just before reaching the end of the runway Aim of the experiment: To study the relationship between the velocity of motion and the angle of inclination Variables: Manipulated: Angle of incline Responding: Velocity just before reaching the end of the runway Constant: Length of runway Apparatus/Materials: Trolley, protractor, wooden blocks, cellophane tape, tickertimer, ticker tape, power supply, friction-compensated runway Setup:
Procedure: 1. The apparatus is set up as per the diagram, and the inclined angle of the plane is measured using a protractor. An initial angle of 5° is used. 2. The ticker-timer is started up and at the same time the trolley is released to slide down the plane. 3. The final velocity when the trolley reaches the end of the plane is calculated using the distance of 10 ticks on the ticker tape. 4. The procedure is repeated by changing the angle of incline to 10°, 15°, 20° and 25°.
Chapter 2: Forces and Motion
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Results: Angle of incline (˚) Final velocity (m s-1) 5 10 15 20 25 Analysis: A graph of the velocity of the trolley against the angle of incline is plotted as follows: Velocity (m s-1)
Angle of incline (°) Conclusion: A higher angle of incline will have a higher velocity at the end of the runway. Hypothesis accepted. Note: The experiment can be modified by making the angle constant and varying the height and length of the runway. Changes must be made accordingly: hypothesis, variable list, procedure, table, analysis, conclusion.
Chapter 2: Forces and Motion
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2.2 INERTIA Option 1: Using a saw blade Hypothesis: The larger the mass, the larger the inertia Aim of the experiment: To study the effect of mass on the inertia of an object Variables: Manipulated: Mass, m Responding: Period of oscillation, T Constant: Stiffness of blade, distance of the centre of the plasticine from the clamp Apparatus/Materials: Jigsaw blade, G-clamp, stopwatch, and plasticine spheres of mass 20 g, 40 g, 60 g, 80 g, and 100 g Setup:
Procedure: 1. One end of the jigsaw blade is clamped to the leg of a table with a G-clamp as per the diagram drawn. 2. A 20 g plasticine ball is fixed at the free end of the blade. 3. The free end of the blade is displaced horizontally and released so that it oscillates. The time for 10 complete oscillations is measured using a stopwatch. This step is repeated. The average of 10 oscillations is calculated. Then, the period of oscillation is determined. 4. Steps 2 and 3 are repeated using plasticine balls with masses 40 g, 60 g, 80 g, and 100 g. 5. A graph of T2 versus mass of load, m is drawn.
Chapter 2: Forces and Motion
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Results: Mass of load, m (g) 20 40 60 80 100
Form 4 Experiments
Time of oscillations, t (s) t1 t2 Average
Physics SPM 2008
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line ing through the origin. This means that the period of oscillation increases with the mass of the load; that is, an object with a large mass has a large inertia. Conclusion: Objects with a large mass have a large inertia. This is the reason why it is difficult to set an object of large mass in motion or to stop it. The hypothesis is valid.
Option 2: Using an inertia balance Hypothesis: The larger the mass, the bigger the inertia Aim of the experiment: To study the effect of mass on the inertia of an object Variables: Manipulated: Mass, m Responding: Period of oscillation, T Constant: Stiffness of the inertia balance Apparatus/Materials: Inertia balance, masses for the inertia balance, G-clamp, stopwatch
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Setup:
Procedure: 1. The inertia balance is set up by clamping it onto one end of the table as shown in the figure above. 2. One mass is placed into the inertia balance. The inertia balance is displaced to one side so that it oscillates in a horizontal plane. 3. The time for 10 complete oscillations is measured using a stopwatch. This step is repeated. The average of 10 oscillations is calculated. Then, the period of oscillation is determined. 4. Steps 2 and 3 are repeated using two and three masses on the inertia balance. 5. A graph of T2 versus number of masses, n is drawn. Results: Number of masses, n 1 2 3
t1
Time of oscillations, t (s) t2 Average
Period of oscillation, T T = t/10 (s) T2 (s2)
Graph of T2 versus m:
Discussion: The graph of T2 versus m shows a straight line ing through the origin. This means that the period of oscillation increases with the mass of the load; that is, an object with a large mass has a large inertia. Conclusion: Objects with a large mass have a large inertia. This is the reason why it is difficult to set an object of large mass in motion or to stop it. The hypothesis is valid. Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
2.3 PRINCIPLE OF CONSERVATION OF MOMENTUM Experiment 1: Elastic collisions Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys colliding with each other elastically Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface of ramp used Apparatus/Materials: Friction-compensated runway, ticker-timer, A.C. power supply, trolleys, wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The runway is adjusted so that it is friction-compensated. 3. Two trolleys of equal mass are selected. A spring-loaded piston is fixed to the front end of trolley A. 4. Two pieces of ticker tape are attached to trolleys A and B respectively with cellophane tape. The ticker tapes are separately ed through the same ticker-timer. 5. The ticker-timer is switched on and trolley A is given a slight push so that it moves down the runway at uniform velocity and collides with trolley B which is stationary. 6. The ticker-timer is switched off when both trolleys reach the end of the runway. 7. From the ticker tapes of trolleys A and B, the final velocities are determined. 8. Momentum is calculated using the formula p = mv. 9. The experiment is repeated using different masses of trolleys.
Chapter 2: Forces and Motion
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Form 4 Experiments
Recording of data: mA mB Before collision uA Initial total momentum, mAuA m m 2m m 2m m 2m 2m
vA
Physics SPM 2008
vB
After collision Final total momentum, mAvA + mBvB
Analysis: From the above table, it is found that: Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Experiment 2: Inelastic collisions Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys colliding with each other inelastically Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface of ramp used Apparatus/Materials: Friction-compensated runway, ticker-timer, A.C. power supply, trolleys, wooden block, ticker tape, cellophane tape, plasticine / Velcro Setup:
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The runway is adjusted so that it is friction-compensated. 3. Two trolleys of equal mass are selected. Plasticine is fixed to the front end of trolley A. (Alternatively, use Velcro pads) 4. A ticker tape is attached to trolley A with cellophane tape. The ticker tape is ed through the ticker-timer. 5. The ticker-timer is switched on and trolley A is given a slight push so that it moves down the runway at uniform velocity and collides with trolley B which is stationary. 6. The ticker-timer is switched off when both trolleys reach the end of the runway. 7. The final velocity is determined from the ticker tape. 8. Momentum is calculated using the formula p = mv. 9. The experiment is repeated using different masses of trolleys. Results: mA mB u m m 2m 2m
Before collision Initial total momentum, mAuA
v
After collision Final total momentum, (mA + mB) v
m 2m m 2m
Analysis: From the above table, it is found that: Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Experiment 3: Explosion Hypothesis: The total momentum before collision is equal to the total momentum after collision, provided there are no external forces acting on the system Aim of the experiment: To demonstrate conservation of momentum for two trolleys moving away from each other from an initial stationary position Variables: Manipulated: Mass of trolleys Responding: Final velocities of the trolleys / Momentum of the trolleys Constant: Surface used
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Apparatus/Materials: Trolleys, wooden blocks, ticker tape, cellophane tape Setup:
Before explosion
After explosion
Procedure: 1. The apparatus is set up as shown in the diagram. 2. Two trolleys A and B of equal mass are placed in with each other on an even and smooth surface. Two wooden blocks are placed on the same row at the end of each trolley respectively. 3. The vertical trigger on trolley B is given a light tap to release the spring-loaded piston which then pushes the trolleys apart. The trolleys collide with the wooden blocks. 4. The positions of the wooden blocks are adjusted so that both the trolleys collide with them at the same time. 5. The distances, dA and dB are measured and recorded. 6. The experiment is repeated with different masses of trolleys. Results: Before explosion Initial total momentum 0 0 0 0
After explosion Mass of trolley A, mA m m 2m 2m
Mass of trolley B, mB m 2m m 2m
Distance traveled by trolley A, dA
Distance traveled by trolley B, dB
Final total momentum, mAdA + mB(-dB)
Analysis: Because both trolleys hit the wooden blocks at the same time, the velocity of the trolleys can be represented by the distance traveled by the trolleys. From the above table, it is found that: Initial total momentum = 0 Final total momentum = 0 ∴ Total momentum before collision = Total momentum after collision Conclusion: Hypothesis proven.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
2.4 FORCE, MASS AND ACCELERATION Experiment 1: Relationship between acceleration and mass when force is constant Hypothesis: When the force applied is constant, the acceleration of an object decreases when its mass increases Aim of the experiment: To study the effect of mass of an object on its acceleration if the applied force is constant Variables: Manipulated: Mass, m Responding: Acceleration, a Constant: Applied force, F Apparatus/Materials: Ticker-timer, A.C. power supply, trolleys, elastic band, runway, wooden block, ticker tape, cellophane tape Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A ticker-tape is attached to the trolley and ed through the ticker-timer. 3. The ticker-timer is switched on and the trolley is pulled down the inclined runway with an elastic band attached to the hind post of the trolley. 4. The elastic band must be stretched to a fix length that is maintained throughout the motion down the runway. 5. When the trolley reaches the end of the runway, the ticker-timer is switched off and the ticker tape is removed. 6. Starting from a clearly printed dot, the ticker tape is divided into strips with each strip containing 10 ticks. 7. A ticker tape chart is constructed, and from the chart, the acceleration of the trolley is calculated. 8. The experiment is repeated using 2 and 3 trolleys. The elastic band must be stretched to the same fixed length as in step 4. Chapter 2: Forces and Motion
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Form 4 Experiments
Results: Mass of trolley, m (kg)
1 m
Physics SPM 2008
Acceleration, a (m s-2)
1 trolley 2 trolleys 3 trolleys Analysis: A graph of a against
1 is drawn. m
a
1 m From the graph, it shows that aα
1 m
Conclusion: The acceleration of an object decreases when the mass increases. Hypothesis proven.
Experiment 2: Relationship between acceleration and force when mass is constant Hypothesis: When the mass is constant, the acceleration of an object increases when the applied force increases Aim of the experiment: To study the effect of force on an object’s acceleration if its mass is constant Variables: Manipulated: Applied force, F Responding: Acceleration, a Constant: Mass, m Apparatus/Materials: Ticker-timer, A.C. power supply, trolleys, elastic band, runway, wooden block, ticker tape, cellophane tape
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A ticker-tape is attached to the trolley and ed through the ticker-timer. 3. The ticker-timer is switched on and the trolley is pulled down the inclined runway with an elastic band attached to the hind post of the trolley. 4. The elastic band must be stretched to a fix length that is maintained throughout the motion down the runway. 5. When the trolley reaches the end of the runway, the ticker-timer is switched off and the ticker tape is removed. 6. Starting from a clearly printed dot, the ticker tape is divided into strips with each strip containing 10 ticks. 7. A ticker tape chart is constructed, and from the chart, the acceleration of the trolley is calculated. 8. The experiment is repeated using 2 and 3 elastic bands. The elastic bands must be stretched to the same fixed length as in step 4. Results: Force applied, F 1 unit 2 units 3 units
Acceleration, a (m s-2)
Analysis: A graph of a against F is drawn. a
F From the graph, it shows that a α F Conclusion: The acceleration of an object increases when the applied force increases. Hypothesis proven.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
2.5 GRAVITATIONAL ACCELERATION Hypothesis: Gravitational acceleration does not depend on an object’s mass Aim of the experiment: To measure the acceleration due to gravity Variables: Manipulated: Mass, m Responding: Gravitational acceleration, g Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply, retort stand, weights (50 g – 250 g), G-clamp, cellophane tape, soft board Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above. 2. One end of the ticker tape is attached to a 50 g weight with cellophane tape, and the other end is ed through the ticker timer. 3. The ticker-timer is switched on and the weight is released so that it falls onto the soft board. 4. The ticker-timer is switched off when the weight lands on the soft board. 5. Gravitational acceleration is calculated from the middle portion of the ticker tape. 6. The experiment is repeated with weights of mass 100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Results: Mass of weights (g) 50 100 150 200 250
Free fall acceleration (m s-2)
Analysis: From the table above, it is found that the gravitational acceleration for all the weights of different masses are the same. Discussion: • The value of the gravitational acceleration, g obtained is less than the standard value of 9.81 m s-2 • This is because the weight is not falling freely. It is affected by: o Air resistance o Friction between ticker tape and ticker-timer Conclusion Gravitational acceleration is not dependent on the mass of the object. Hypothesis proven.
2.6 PRINCIPLE OF CONSERVATION OF ENERGY Hypothesis: Energy cannot be created or destroyed, it can only change form. Aim of the experiment: To investigate the conversion of gravitational potential energy to kinetic energy. Variables: Manipulated: Mass, m Responding: Final velocity, v Constant: Height, h Apparatus/Materials: Ticker-timer, ticker tape, A.C. power supply, trolley, thread, weights, smooth pulley, friction-compensated runway, soft board, cellophane tape
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Setup:
Procedure: 1. Apparatus is setup as shown in the diagram above. 2. One end of the ticker tape is attached to the back of the trolley with cellophane tape and the other end is ed through the ticker-timer. 3. The ticker-timer is switched on, and the trolley is released. 4. The final velocity of the trolley and the weight is determined from the ticker tape obtained. 5. The experiment is repeated with different masses of trolleys and weights. Results: Mass of trolley = M kg Mass of weight = m kg Height of weight before release = h m Final velocity of trolley and weight = v m s-1 Loss of potential energy of the weight = mgh Final kinetic energy of the trolley and the weight = ½ (M + m) v2 It is found that ½ (M + m) v2 = mgh Conclusion The loss of potential energy is converted to kinetic energy. Hypothesis proven. Note: The experiment can be modified by making the mass constant and changing the height of the weight’s release. Changes must be made to the variables list and to the last step of the procedure.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
2.7 HOOKE’S LAW Hypothesis: The bigger the weight, the longer the spring extension Aim of the experiment: To determine the relationship between the weight and the spring extension Variables: Manipulated: Weight of the load Responding: Spring extension Constant: Spring constant Apparatus and Materials: Spring, pin, weights, plasticine, retort stand, metre rule Setup:
Procedure: 1. The apparatus is setup as shown in the diagram. 2. The length of the spring without any weights, l0 is measured using the metre rule with the pin as reference. 3. A 50 g weight is hung from the bottom of the spring. The new length of the spring, l is measured. The spring extension is l – l0. 4. Step 4 is repeated with weights 100 g, 150 g, 200 g, and 250 g.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
Results: Original length of spring = l0 = __________ cm Load mass (g) 50 g 100 g 150 g 200 g 250 g
Load weight (N) 0.5 N 1.0 N 1.5 N 2.0 N 2.5 N
Spring length, l (cm)
Spring extension, x = l – l0 (cm)
Analysis: A graph of spring extension, x against weight, F is plotted. x
F The x-F graph is a linear graph which es through the origin. This shows that the extension of the spring is directly proportional to the stretching force. Conclusion: Hypothesis proven.
Chapter 2: Forces and Motion
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Form 4 Experiments
Physics SPM 2008
CHAPTER 3: FORCES AND PRESSURE 3.1 PRESSURE IN LIQUIDS Experiment 1: Water pressure and depth Hypothesis: Water pressure increases with depth Aim of the experiment: To find the relationship between the pressure in a liquid according to its depth Variables: Manipulated: Depth of liquid Responding: Pressure in liquid Constant: Density of liquid Apparatus and Materials: Measuring cylinder, thistle funnel, rubber tube, manometer, metre rule Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. The measuring cylinder is completely filled with water. 3. The thistle funnel is lowered into the water to a depth of 10.0 cm. The manometer reading is measured. The difference in the liquid heights in the manometer represent the pressure reading. 4. Step 3 is repeated with values of depth 20.0 cm, 30.0 cm, 40.0 cm and 50.0 cm.
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
Results: Depth (cm) Manometer reading (cm) 10.0 20.0 30.0 40.0 50.0
Analysis: A graph of pressure against depth is drawn. Pressure
Depth Conclusion: It is observed that the manometer reading increases as the depth of the thistle funnel increases. This shows that the pressure increases with the depth of the liquid. Hypothesis proven.
Experiment 2: Water pressure and density Hypothesis: Pressure in liquid increases with its density Aim of the experiment: To find the relationship between the pressure in a liquid and its density Variables: Manipulated: Density of liquid Responding: Pressure in liquid Constant: Depth of liquid Apparatus and Materials: Measuring cylinder, thistle funnel, rubber tube, manometer, metre rule, water, glycerin, alcohol
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. The measuring cylinder is completely filled with water. 3. The thistle funnel is lowered into the water to a depth of 50.0 cm. The manometer reading is measured. The difference in the liquid heights in the manometer represent the pressure reading. 4. The experiment is repeated by replacing the water with glycerin (density = 1300 kg m-3) and alcohol (density = 800 kg m-3). Results: Depth within liquid = 50.0 cm Liquid Density (kg m-3) Manometer reading (cm) Water 1000 Glycerin 1300 Alcohol 800
Conclusion: It is observed that the manometer reading increases as the density of the liquid increases. This shows that the pressure increases with the density of the liquid. Hypothesis proven.
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
3.2 ARCHIMEDES’ PRINCIPLE Hypothesis: The buoyant force on an object in a liquid is equal to the weight of the liquid displaced Aim of the experiment: To find the relationship between the buoyant force acting upon an object in a liquid and the weight of the liquid displaced Variables: Manipulated: Weight of the object Responding: Buoyant force / Weight of liquid displaced Constant: Density of liquid used Apparatus and Materials: Eureka tin, spring balance, stone, thread, beaker, triple beam balance Setup:
Procedure: 1. A beaker is weighed with the triple beam balance and its mass, m1 is recorded. 2. The Eureka tin is filled with water right up to the level of the overflow hole. The beaker is placed beneath the spout to catch any water that flows out. 3. A stone is suspended from the spring balance with thread and its weight in air, W1 is read from the spring balance.
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
4. The stone is lowered into the Eureka tin until it is completely immersed in water without touching the bottom of the Eureka tin. The water will overflow into the beaker. 5. The spring balance reading, W2 is recorded. 6. The beaker with water is weighed with the triple beam balance, and the mass, m2 is recorded. Results: Weight of stone in air = W1 Weight of stone in water = W2 Buoyant force acting on the stone = W2 – W1 Weight of the empty beaker = m1g Weight of the beaker and displaced water = m2g Weight of the displaced water = (m2 – m1)g It is found that W2 – W1 = (m2 – m1)g Discussion: The loss of weight of the stone immersed in water is due to the buoyant force of the water acting upon it. From the results, it is found that the loss in weight of the stone is equal to the weight of water displaced. Conclusion: Buoyant force on the stone = Weight of the water displaced by the stone Hypothesis proven. Note: Experiment can be modified to compare the weight of different sized stones and the values of buoyant force
3.3 PASCAL’S PRINCIPLE Hypothesis: The liquid pressure exerted on a small surface is equal to the liquid pressure exerted on a large surface in a closed system Aim of the experiment: To find the relationship between the pressure in a small syringe and a large syringe in a closed system Variables: Manipulated: Pressure acting on the small syringe Responding: Pressure acting on the large syringe Constant: Density of liquid within the system
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
Apparatus and Materials: 5 ml syringe, 10 ml syringe, several weights, rubber tube, two retort stands Setup:
Procedure: 1. The diameters of the piston of both syringes are measured and their cross-sectional areas are calculated. 2. The two syringes are each mounted on a retort stand. 3. The syringes are filled with water and are securely connected to each other with a rubber tube as shown in the diagram. 4. A weight is placed on the piston of the small syringe. 5. Weights are added to the piston of the large syringe until the water levels in the two syringes are the same (i.e. syringes are in equilibrium). 6. The forces, F1 and F2 on the syringes are calculated. 7. The pressure, P1 and P2 exerted on the syringes are compared. Results: Syringe size
Cross-sectional area, A
Mass of the weight, m
Force exerted on the syringe, F = mg
Small Large
A1 A2
m1 m2
F1 F2
Pressure, P F = A P1 P2
Discussion: It is found that the pressure, P1 exerted on the piston of the small syringe is equal to the pressure, P2 exerted on the piston of the large syringe. Conclusion: The water pressure exerted on the piston of the small syringe is equal to the water pressure exerted on the piston of the large syringe. This shows that the pressure applied to the piston of the small syringe is transmitted to the piston of the large syringe. Hypothesis proven.
Chapter 3: Forces and Pressure
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Form 4 Experiments
Physics SPM 2008
3.4 BERNOULLI’S PRINCIPLE Hypothesis: When the velocity of water increases, its pressure decreases and vice versa. Aim of the experiment: To find the effects of movement on the pressure exerted by a fluid Variables: Manipulated: Velocity of the water Responding: Pressure of the water Constant: Density of the water Apparatus and Materials: Uniform glass tube, Venturi tube, rubber hose, water from a tap Procedure: 1. A uniform glass tube is connected to a tap with a rubber hose. The other end of the tube is closed up with a stopper. 2. The tap is opened slowly so that water flows into it. 3. The levels of the vertical tubes are observed. 4. The stopper is then removed. The tap is adjusted so that the water flows through the tube at a uniform rate. 5. The levels of the vertical tubes are observed. 6. The experiment is repeated by replacing the uniform glass tube with a Venturi tube. Results: Uniform glass tube:
With the stopper
Chapter 3: Forces and Pressure
Without the stopper
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Venturi tube:
With the stopper
Without the stopper
Discussion: • The height of the water in the vertical tube represents the pressure at that point. • When water is not flowing, the pressure along the entire tube is the same, therefore the water levels in all three vertical tubes are the same. • For the uniform glass tube: o Water flows from high pressure to low pressure. o Therefore, the water levels are decreasing because the pressure is decreasing. • For the Venturi tube: o The velocity at Y is higher because of the smaller cross-sectional area. o Therefore, the pressure at Y is the lowest. o Pressure still decreases from X to Z because water flows from high pressure to low pressure. Conclusion: The higher the water velocity, the lower the pressure at that point. Hypothesis proven.
Chapter 3: Forces and Pressure
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Physics SPM 2008
CHAPTER 4: HEAT AND ENERGY 4.1 SPECIFIC HEAT CAPACITY Experiment 1: Rise in temperature – varying mass, fixed amount of heat Hypothesis: The bigger the mass of water, the smaller the rise in temperature when supplied with the same amount of heat Aim of the experiment: To determine the rise in temperature of water with varying masses Variables: Manipulated: Mass of water, m Responding: Rise in temperature, θ Constant: Amount of heat supplied, Q Apparatus and Materials: Beaker, electric heater, thermometer, stopwatch, triple beam balance, stirrer, polystyrene sheet, felt cloth Set up:
Procedure: 1. With the help of a triple beam balance, fill a beaker with water of mass 0.40 kg. 2. The apparatus is set up as shown in the diagram. 3. The initial temperature of the water, θ1 is measured using a thermometer and is recorded. 4. The electric heater is placed into the water and is switched on for 1 minute. The water is continuously stirred. 5. The water is continuously stirred even after the heater has been switched off. The
Chapter 4: Heat and Energy
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6. The highest temperature the water reaches, θ2 is measured and recorded. The rise in temperature, θ = θ2 – θ1 is calculated. 7. The experiment is repeated with water of mass 0.50 kg, 0.60 kg, 0.70 kg, and 0.80 kg. 1 8. A graph of θ against m and a graph of θ against are plotted. m Results: Mass of water, Initial Final Rise in 1 (kg-1) m (kg) temperature, temperature, temperature, θ m θ1 (°C) θ2 (°C) = θ2 – θ1 (°C) 0.40 0.50 0.60 0.70 0.80
Analysis: • The amount of heat supplied is made constant by using the same heater for the same period of time. • The following graphs are obtained:
Conclusion: The rise in temperature is inversely proportional to the mass when a constant amount of heat is supplied. Hypothesis proven.
Experiment 2: Rise in temperature – fixed mass, varying amount of heat Hypothesis: When more heat is supplied to water of fixed mass, the rise in temperature is greater Aim of the experiment: To determine the rise in temperature of water with varying amounts of heat Variables: Manipulated: Amount of heat supplied, Q Responding: Rise in temperature, θ Constant: Mass of water, m
Chapter 4: Heat and Energy
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Apparatus and Materials: Beaker, electric heater, thermometer, stopwatch, triple beam balance, stirrer, polystyrene sheet, felt cloth Set up:
Procedure: 1. With the help of a triple beam balance, fill a beaker with water of mass 0.50 kg. 2. The apparatus is set up as shown in the diagram. 3. The initial temperature of the water, θ1 is measured using a thermometer and is recorded. 4. The electric heater is placed into the water and is switched on for 1 minute. The water is continuously stirred. 5. The water is continuously stirred even after the heater has been switched off. 6. The highest temperature the water reaches, θ2 is measured and recorded. The rise in temperature, θ = θ2 – θ1 is calculated. 7. The experiment is repeated with water of the same mass but with heating time of 2 minutes, 3 minutes, and 4 minutes. 8. A graph of θ against t is plotted. Results: Heating time (minute)
Initial temperature, θ1 (°C)
Final temperature, θ2 (°C)
Rise in temperature, θ = θ2 – θ1 (°C)
1 2 3 4 Analysis: • Because the same heater with fixed power is used, the heating time, t is defined operationally as the heat quantity. • The following graph is obtained:
Chapter 4: Heat and Energy
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Conclusion: When an object of fixed mass is heated, the rise in temperature changes proportionally to the amount of heat supplied. Hypothesis proven.
Experiment 3: Determining the specific heat capacity of aluminium Aim of the experiment: To determine the specific heat capacity of aluminium Apparatus and Materials: Aluminium cylinder, weighing scale, electric heater, thermometer, power supply, felt cloth, polystyrene sheet, stopwatch, lubricating oil Set up:
Procedure: 1. An aluminium cylinder with two cavities is weighed and its mass, m is recorded. 2. The electrical power of the heater, P is recorded. 3. The electrical heater is then placed inside the large cavity in the centre of the cylinder. 4. The thermometer is then placed in the small cavity of the aluminium cylinder. 5. A few drops of lubricating oil are added to both cavities to ensure good thermal (better heat transfer). 6. The apparatus is set up as shown in the diagram above. 7. The initial temperature of the aluminium cylinder, θ1 is recorded. 8. The electric heater is switched on and the stopwatch is started simultaneously. 9. After heating for t seconds, the heater is switched off. The highest reading on the thermometer, θ2 is recorded. 10. The experiment is repeated and an average value of c is calculated.
Chapter 4: Heat and Energy
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Physics SPM 2008
Results: Electric power of heater = P Watt Heating time = t seconds Mass of aluminium cylinder = m kg Initial temperature of the aluminium cylinder = θ1 Final temperature of the aluminium cylinder = θ2 Temperature rise = θ2 – θ1 Electrical energy supplied by the heater = Pt Heat energy absorbed by the aluminium cylinder = mcθ On the assumption that there is no heat loss to the surroundings: Heat supplied = Heat absorbed Pt = mcθ Pt Specific heat capacity, c = mθ Discussion: • The aluminium cylinder is wrapped with a felt cloth to reduce the heat loss to the surroundings and the polystyrene sheet acts as a heat insulator to avoid heat loss to the surface of the table. • The value of the specific heat capacity of aluminium, c determined in the experiment is larger than the standard value. This is because there will be some heat lost to the surrounding. • The temperature of the aluminium cylinder will continue to rise after the electrical heater has been switched off because there is still some heat transfer from the heater to the cylinder. Conclusion: The specific heat capacity of aluminium is a constant.
4.2 SPECIFIC LATENT HEAT Experiment 1: Heating of naphthalene Hypothesis: During the change of state of naphthalene from solid to liquid, there is no change in temperature when heat is continuously supplied Aim of the experiment: To observe the change in temperature when naphthalene is melting Apparatus and Materials: Boiling tube, naphthalene powder, beaker, thermometer, Bunsen burner, stopwatch, retort stand, tripod stand, wire gauze Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Set up:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The initial temperature of the naphthalene is recorded. 3. The Bunsen burner is lighted and the stopwatch started. 4. The temperature of the naphthalene is recorded at 1 minute intervals until the temperature reaches 100°C. 5. The state of the naphthalene is observed and tabulated throughout the heating process. 6. A graph of temperature against time is drawn. Results: Time, t (minute) Temperature of naphthalene, θ (°C) 0 1 2 3 …
Graph of temperature against time:
Discussion: • The temperature-time graph shows that the temperature of naphthalene rises until the naphthalene starts to melt. • The naphthalene starts to melt at 80°C. The temperature remains constant at this value for several minutes while the naphthalene continues to melt with the heat.
Chapter 4: Heat and Energy
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•
Form 4 Experiments
Physics SPM 2008
After the naphthalene has completely melted, the temperature begins to rise with continued heating.
Conclusion: The temperature of the naphthalene remains constant during a change of state from solid to liquid.
Experiment 2: Cooling of naphthalene Hypothesis: During the change of state of naphthalene from liquid to solid, there is no change in temperature Aim of the experiment: To observe the change in temperature when naphthalene is freezing Apparatus and Materials: Boiling tube, naphthalene powder, beaker, thermometer, Bunsen burner, stopwatch, retort stand, tripod stand, wire gauze Set up:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The naphthalene is heated until the temperature reaches 95°C. 3. The boiling tube is then removed from the water bath and the outer part of the tube is dried. 4. The temperature of the naphthalene is recorded every minute until the temperature drops to about 60°C. 5. A graph of temperature against time is drawn.
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Results: Time, t (minute) Temperature of naphthalene, θ (°C) 0 1 2 3 …
Graph of temperature against time:
Discussion: • The temperature-time graph shows that the temperature of naphthalene drops until 80°C where it stays constant for several minutes as it freezes. • After the naphthalene has completely frozen, the temperature continues to drop. Conclusion: The temperature of the naphthalene remains constant during a change of state from liquid to solid.
Experiment 3: Latent heat of fusion (ice) Aim of the experiment: To determine the latent heat of fusion of ice Apparatus and Materials: Pure ice, electric immersion heater, filter funnel, beaker, stopwatch, weighing balance, power supply, retort stand, clamp
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Set up:
Set A
Set B
Procedure: 1. The mass of two empty beakers, A and B are determined using the weighing balance. 2. The apparatus is arranged as shown in the diagram above. 3. Each of the two filter funnels is filled with ice cubes. 4. The immersion heater in Set A, the control experiment, is not connected to the power supply. The purpose of Set A is to determine the mass of the ice melted by the surrounding heat. The heater in Set B is switched on. 5. When water starts to drip from the filter funnels at a steady rate, the stopwatch is started and the empty beakers A and B are placed beneath the filter funnels. 6. After a period of t seconds, the heater B is switched off. The masses of both beakers, A and B are determined using the weighing balance. 7. The experiment is repeated to get an average value. Results: Set A: Mass of empty beaker = mA1 kg Mass of beaker + water = mA2 kg Mass of ice melted by surrounding heat, ma = mA2 – mA1 kg Set B: Mass of empty beaker = mB1 kg Mass of beaker + water = mB2 kg Mass of ice melted by surrounding heat & immersion heater, mb = mB2 – mB1 kg Mass of ice melted by the electric immersion heater, m = mb – ma kg Electrical energy supplied by the electrical immersion heater, E = Pt Heat energy absorbed by the ice during melting, Q = mL Assuming there is no heat loss to the surroundings: Electrical energy supplied = Heat energy absorbed by the melting ice Pt = mL Pt Specific latent heat of fusion of ice, L = m Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Discussion: • The purpose of Set A, the control experiment, is to determine the mass of ice melted by the surrounding heat. • The immersion heater must be fully immersed in the ice cubes to avoid or reduce heat loss. • The stopwatch is not started simultaneously when the immersion heater is switched on because the immersion heater requires a time period before reaching a steady temperature. At this point, the rate of melting of ice will be steady. • The value of the specific latent heat of fusion of ice, L obtained in this experiment is higher than the standard value because part of the heat supplied by the heater is lost to the surroundings. Conclusion: The specific latent heat of fusion of ice is a constant.
Experiment 4: Latent heat of vapourisation (water) Aim of the experiment: To determine the latent heat of vapourisation of water Apparatus and Materials: Pure water, electric immersion heater, filter funnel, beaker, stopwatch, weighing balance, power supply, retort stand, clamp Set up:
Procedure: 1. The apparatus is set up as shown in the diagram above. 2. A beaker is placed on the platform of the electronic weighing balance. 3. The electric heater is fully immersed in the water and held in this position by being clamped to a retort stand. 4. The electric heater is switched on to heat the water to its boiling point. 5. When the water starts to boil at a steady rate, the stopwatch is started and the reading on the electronic balance, m1 is recorded. 6. The water is allowed to boil for a period of t seconds. 7. At the end of the period of t seconds, the reading on the electronic balance, m2 is recorded.
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Results: Electrical power of heater = P Watt Time period of boiling = t seconds Electrical energy supplied by the electrical immersion heater, E = Pt Mass of water vapourised = m2 – m1 Heat energy absorbed by the water during vapourisation, Q = mL Assuming there is no heat loss to the surroundings: Electrical energy supplied = Heat energy absorbed by the vapourized water Pt = mL Pt Specific latent heat of vapourization of water, L = m Discussion: • The immersion heater must be fully immersed in the water to avoid or reduce heat loss. • The stopwatch is not started simultaneously when the immersion heater is switched on because the immersion heater requires a time period before reaching a steady temperature. At this point, the rate of heating of water will be steady. • The value of the specific latent heat of vapourization of water, L obtained in this experiment is higher than the standard value because part of the heat supplied by the heater is lost to the surroundings. Conclusion: The specific latent heat of vapourization of water is a constant.
4.3 BOYLE’S LAW Option 1: Changing the volume of air to measure pressure Hypothesis: When the volume of air decreases, the pressure increases when its mass and temperature is constant Aim: To investigate the relationship between the pressure and volume of air Variables: Manipulated: Volume of air within syringe Responding: Pressure of air Constant: Mass, temperature of air Apparatus and Materials: Rubber hose, Bordon gauge, 100 cm3 syringe Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The nose of the syringe is fitted with a rubber hose and the piston is adjusted so that air volume of 100 cm3 at atmospheric pressure is trapped in the syringe. 3. The rubber hose is connected to a Bourdon gauge and air pressure is read from the gauge. 4. The piston of the syringe is pushed in until the trapped air volume becomes 90 cm3 and the air pressure is read from the Bourdon gauge. 5. Step 4 is repeated for air volume values 80, 70, and 60 cm3. Results: Volume, V (cm3)
1 (cm-3) V
Pressure, P (Pa)
100 90 80 70 60 Analysis: • • •
1 is plotted. V A linear graph going through the origin is obtained. This indicates that pressure is inversely proportional to the volume of gas. A graph of P against
Conclusion: Gas pressure of fixed mass is inversely proportional to its volume.
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Option 2: Changing the pressure of air to measure volume Hypothesis: When the pressure of air decreases, the volume increases when its mass and temperature is constant Aim: To investigate the relationship between the pressure and volume of air Variables: Manipulated: Pressure of air Responding: Volume of air trapped in the capillary tube Constant: Mass, temperature of air Apparatus and Materials: Bicycle pump, ruler, tank with oil, pressure gauge, glass tube Set up:
Procedure: 1. The apparatus is set up as shown in the diagram above. 2. The piston of the bicycle pump is pushed in to compress the air inside the glass tube until the pressure is 10 kPa. 3. When the reading on the pressure gauge is P, the volume of the air column, V is recorded. 4. Steps 1 and 2 are repeated for 5 pressure readings of 20 kPa, 30 kPa and 40 kPa.
Chapter 4: Heat and Energy
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Form 4 Experiments
Results: Pressure, P (kPa)
1 (Pa-1) P
Physics SPM 2008
Volume, V (cm3)
10 20 30 40 Analysis: • • •
1 is plotted. P A linear graph going through the origin is obtained. This indicates that pressure is inversely proportional to the volume of gas. A graph of V against
Conclusion: Volume of gas of fixed mass is inversely proportional to its pressure.
4.4 CHARLES’ LAW Hypothesis: When the temperature of air increases, the volume increases if the mass and pressure is constant Aim: To investigate the relationship between the volume and the temperature of gas Variables: Manipulated: Air temperature Responding: Air volume Constant: Mass and pressure of the trapped air Apparatus and Materials: Capillary tube, tall beaker, thermometer, Bunsen burner, tripod, wire gauze, retort stand, mercury or concentrated sulphuric acid, stirrer, ruler, ice, rubber band
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Set up:
Procedure: 1. Apparatus is set up as per the diagram. 2. The air to be studied is trapped in a capillary tube by concentrated sulphuric acid. 3. The capillary tube is fitted to a ruler using two rubber bands and the bottom end of the air column is ensured to match the zero marking on the ruler. 4. Water and ice is poured into the beaker until the whole air column is submerged. Water is then stirred until the temperature rises to 10 °C. The length of the air column and the temperature of the water are recorded. 5. Water is heated slowly while being stirred continuously. The length of the air column is recorded every 10 °C until the water temperature reaches 90 °C. Results: 10 20 30 40 50 60 70 80 90 Temperature, θ (°C) Length of air column, x (cm) Analysis: • A graph of x against θ is plotted. • A linear graph is obtained. • When extrapolated, length x = 0 occurs when gas temperature, θ = -273 °C
•
When the Celsius scale is replaced with the Kelvin scale, a linear graph that goes through origin is obtained.
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
Discussion: From the graph plotted, it is found that the length of the air column, x is directly proportional to its temperature, T (K). Because gas volume is directly proportional to the length of the column, it also indicates that gas volume is directly proportional to its absolute temperature. Conclusion: Gas volume of fixed mass is directly proportional to its absolute temperature
4.5 PRESSURE LAW Hypothesis: When the temperature of air increases, the pressure increases if the mass and volume is constant Aim: To investigate the relationship between the pressure and the temperature of gas Variables: Manipulated: Air temperature Responding: Air pressure Constant: Mass and volume of the trapped air Apparatus and Materials: Round-bottomed flask, mercury thermometer, Bourdon gauge, Bunsen burner, tripod, wire gauze, retort stand, stirrer, ice Set up:
Chapter 4: Heat and Energy
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Hoo Sze Yen
Form 4 Experiments
Physics SPM 2008
Procedure: 1. Apparatus is set up as per the diagram. 2. The round-bottomed flask is submerged in water and the water bath with ice is stirred continuously until the temperature of the water bath is stable. 3. The temperature of the water is taken from the thermometer. 4. The reading from the Bourdon gauge is read at temperatures 30, 40, 50, 60, 70 and 80 °C. Results: Temperature, θ (°C) 30 40 50 60 70 80 Air pressure, P (Pa) Analysis: • A graph of P against θ is plotted. • A linear graph is obtained. • When extrapolated, pressure P = 0 occurs when gas temperature, θ = -273 °C
•
When the Celsius scale is replaced with the Kelvin scale, a linear graph that goes through origin is obtained.
Conclusion: Gas pressure of fixed mass is directly proportional to its absolute temperature
Chapter 4: Heat and Energy
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Form 4 Experiments
Physics SPM 2008
CHAPTER 5: LIGHT AND VISION 5.1 REFLECTION Hypothesis: The angle of reflection is equal to the angle of incidence Aim of the experiment: To study the relationship between the angle of incidence and angle of reflection Variables: Manipulated: Angle of incidence, i Responding: Angle of reflection, r Constant: Plane mirror used Apparatus/Materials: Light box, plane mirror, plasticine, paper, pencil, protractor Setup:
Procedure: 9. A straight line, PQ is drawn on a sheet of white paper. 10. The normal line, ON is drawn from a point at the centre of PQ. 11. With the aid of a protractor, lines at angles of incidence 15°, 30°, 45°, 60° and 75° to the normal line, are drawn to its left. 12. A plane mirror is erected along the line PQ. It is secured in this position with the aid of plasticine. 13. A ray of light from the ray box is directed along the 15° line. Two positions are marked with a pencil on the line of the reflected ray. 14. Step 5 is repeated for the other angles of incidence. 15. The plane mirror is removed. The reflected rays are drawn by ing the respective marks. 16. The angles of reflection corresponding with all the angle of incidence are measured. The results are tabulated.
Chapter 5: Light and Vision
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Physics SPM 2008
Results: Incident angle (˚) Reflected angle (˚) 15 30 45 60 75
Conclusion: The angle of incidence is equal to the angle of reflection.
5.2 CURVED MIRRORS Aim of the experiment: To study the characteristics of images formed by curved mirrors Apparatus/Materials: Concave mirror, convex mirror, plasticine, light bulb mounted on a wooden block, metre rule, white screen Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The focal length, f and the radius of curvature, r of the concave mirror, as supplied, are recorded. 3. The light bulb is positioned at a distance greater than the radius of curvature of the mirror, i.e. u > 2f. The white screen is moved between the concave mirror and the light bulb until an image is clearly focused on the screen. The image distance, v is measured by a metre rule and recorded. 4. Step 3 is repeated with the light bulb positioned at C (u = 2f), between C and F (f < u < 2f), at F (u = f), and between F and P (u < f).
Chapter 5: Light and Vision
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Form 4 Experiments
Physics SPM 2008
5. The values of u, v, and the characteristics of the images formed are recorded in a table. 6. The experiment is repeated by replacing the concave mirror with a convex mirror. Results: Concave mirror; Position of Object object distance, u (cm)
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual Inverted Magnified / Same size
Beyond C (u > 2f) At C (u = 2f) Between C and F (f < u < 2f) At F (u = f) Between F and P (u < 2f) Convex mirrors: For all positions, the image characteristics are: __________________________ Conclusion: • For concave mirrors, images formed can be real or virtual, whereas for convex mirrors, only virtual images are formed. • The characteristics of images formed by the concave mirror depend on the position of the object.
5.3 REFRACTION Hypothesis: The refracted light ray obeys Snell’s Law which states that the value of
sin i is a sin r
constant where i is the angle of incidence and r is the angle of refraction
Aim of the experiment: To study the relationship between the angle of incidence and angle of refraction
Chapter 5: Light and Vision
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Form 4 Experiments
Physics SPM 2008
Variables: Manipulated: Angle of incidence, i Responding: Angle of refraction, r Constant: Plane mirror used Apparatus/Materials: Ray box, glass block, paper, pencil Setup:
Procedure: 1. The outline of the glass block is traced on a sheet of white paper and labeled. 2. The glass block is removed. Point O is marked on one side of the glass block. With a protractor, lines forming angles of incidence 20°, 30°, 40°, 50° and 60° are drawn and marked. 3. The glass block is replaced on its outline on the paper. 4. A ray of light from the ray box is directed along 20° line. The ray emerging on the other side of the block is drawn. 5. Step 4 is repeated for the other angles of incidence. 6. The glass slab is removed. The points of incidence and the corresponding points of emergence are ed. The respective angles of refraction are measured with a protractor. sin i 7. The values of sin i, sin r, and are calculated. sin r Results: Angle of incidence, i (°) Angle of refraction, r (°) Sin i Sin r
n=
sin i sin r
20 30 40 50 60 Conclusion: It is found that
sin i is a constant. Hypothesis valid. sin r
Chapter 5: Light and Vision
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Form 4 Experiments
Physics SPM 2008
5.4 ACTUAL DEPTH & APPARENT DEPTH Hypothesis: The deeper the actual depth, the deeper the apparent depth Aim of the experiment: To study the relationship between the actual depth and apparent depth Variables: Manipulated: Actual depth, D Responding: Apparent depth, d Constant: Refractive index of medium (water), n Apparatus/Materials: Tall beaker, 2 pins, ruler, metre rule, retort stand Setup:
Procedure: 1. Apparatus is set up as shown in the diagram. 2. A pin is mounted on a movable clamp on a retort stand. 3. Another pin is placed at the base of the tall beaker. Water is filled as the actual depth to D = 7.0 cm. 4. The object pin O is observed from the top, and pin I is adjusted vertically until it appears to meet pin O. At this point, the position of pin I matches the apparent depth, d of pin O. The apparent depth is measured from the top of the water level to the position of pin I. 5. Step 4 is repeated by changing the actual depth to 9.0 cm, 11.0 cm, 13.0 cm and 15.0 cm. 6. The results are tabulated and a graph of D against d is plotted.
Chapter 5: Light and Vision
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Form 4 Experiments
Physics SPM 2008
Results: Actual depth, D (cm) Apparent depth, d (cm) 7.0 9.0 11.0 13.0 15.0
Analysis: A linear graph that goes through origin is obtained. D
d Discussion: • The gradient of the graph is equal to the index of refraction of water. Conclusion: Hypothesis is valid
5.5 TOTAL INTERNAL REFLECTION Aim of the experiment: To determine the critical angle of glass Apparatus/Materials: Semicircular glass block, ray box, protractor, white paper, pencil Setup:
Procedure: 1. A semicircular glass block is placed on a sheet of white paper. The outline of the glass block is traced onto the paper with a sharp pencil. Chapter 5: Light and Vision
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2. The glass block is put aside. A normal line, NN’ is drawn through the centre point, O on the diameter. 3. The glass block is replaced on its outline. 4. A narrow beam of light from the ray box is directed at point O at a small angle of incidence. The refracted and reflected rays are observed. 5. The angle of incidence, i measured from the normal line is adjusted until the light ray is refracted along the length of the air-glass boundary. The point of entry of the light ray is marked and measured with a protractor. At this point, the incident angle is known as the critical angle, c. 6. The angle of incidence is increased and the resultant rays are observed. 7. The experiment is repeated by pointing the light ray through the other side of the semicircle. Results: • When i < c, part of the light ray is refracted to the air, and part of it will be reflected back within the glass block • When i = c, the light ray will be refracted along the length of the glass-air boundary • When i > c, no refraction occurs; all the light ray will be totally internally reflected within the glass block Analysis: The critical angle, c is a constant. 1 Refractive index of glass, n = sin c Conclusion: The refractive index of glass, n =
1 sin c
5.6 LENSES Hypothesis: The image produced by a convex lens is virtual or real depending on the position of the object. The characteristics of an image produced by a concave lens is not affected by the object distance. Variables: Manipulated: Object distance, u Responding: Image distance, v Constant: Focal length of lens, f Apparatus/Materials: Cardboard with a cross-wire in triangular cut-out, light bulb, lens holder, convex lens, concave lens, white screen
Chapter 5: Light and Vision
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Form 4 Experiments
Physics SPM 2008
Setup:
Procedure: 1. The apparatus is set up as shown in the diagram. 2. The focal length, f of the convex lens supplied is recorded. 3. The object (triangle with a cross-wire) is placed at a distance greater than 2f from the convex lens. 4. The white screen is moved back and forth until a sharp image of the triangle is formed on the screen. The image distance, v is measured. The characteristics of the image are observed and recorded in a table. 5. Step 3 is repeated wit the object distances, u = 2f, f < u < 2f, u = f, and u < f. 6. For positions where the image cannot be formed on the screen, the screen is removed and the image is viewed through the lens from the other side of the lens. 7. The experiment is repeated by replacing the convex lens with a concave lens. Results: Convex lens: Position Object of object distance, u (cm)
Image distance, v (cm)
Characteristics of image Real / Upright / Diminished / Virtual Inverted Magnified / Same size
u > 2f u = 2f f < u < 2f u=f u < 2f Concave lens: For all positions, the image characteristics are: __________________________ Conclusion: • For convex lenses, images formed can be real or virtual, whereas for concave lenses, only virtual images are formed. • The characteristics of images formed by the convex lens depend on the position of the object.
Chapter 5: Light and Vision
Page 52 of 52
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