SECTION A (25 MARKS)
Answer all the questions in this section in the spaces provided.
Figure 1 shows the vernier scale of a vernier calliper.
On the figure, include the main scale so that the vernier calliper shows a reading of 3.15cm.
2. Explain why weight of an object is a vector quantity. (1 mark)
It has both magnitude which is measured in Newtons and direction which is always directed to the center of the earth.
3. Figure 2 shows the shape of a bimetallic strip made of metals A and B when heated.
State the reason why the strip appears as shown.
Metal A expands faster than metal B.
4. It is observed that in order to balance a sea-saw, the heavier child sits closer to the pivot. State the reason for this observation.
The heavier sits closer to the pivot to reduce moment produced by his weight.
Moment of a force is given by Force × Perpendicular distance from the pivot.
5. Explain one way in which a person maintains stability when carrying a bucket of water in one hand.
By leaning his body in the opposite direction of the bucket to shift his center of gravity.
6. Figure 3 shows a simple hand sanitizer dispenser
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Explain how it works. (3 marks)
Pressing the pump compresses air inside the bottle.
The increased air pressure forces the sanitizer through the nozzle.
Releasing the pump allows air to flow back into the bottle, preparing it for the next use.
7. Figure 4 shows a marble that was set into oscillations released in a when bowl.
On the axes provided, sketch the velocity-time graph for the motion of the marble in one complete oscillation.
Question 8:
State the meaning of the term viscosity as used in fluids. (1 mark)
Is the measure to the fluid's resistance to flow. OR (Is the measure of the internal friction between fluid layers/particles)
Question 9:
A machine raises a mass of 20 kg through a distance of 0.2 m when an effort of 100 N is moved through a distance of 0.32 m. determine the velocity ratio of the machine. (2 marks)
VR = Distance moved by effort Distance moved by the load
0.32 0.2 = 1.6
Question 10:
A gas bubble is released at the bottom of a pond containing water. It is observed that as the bubble rises to the water surface, it expands. Explain this observation. (2 marks)
As the bubble rises, the pressure of the surrounding water decreases. This allows the gas to expand since the internal pressure becomes greater than the external pressure.
Question 11:
A stone of mass 200 g is tied at the end of a string 1 m long is whirled in a horizontal circle at an angular velocity of 10 radians per second. Determine the centripetal force acting on the stone. (3 marks)
Fc = mω²r
= 0.2 x 10² x 1
= 20 N
Question 12:
An object is released into a eureka can full of water. It is observed that the weight of the displaced water is equal the weight of the object. Explain this observation. (2 marks)
The object displaces a volume of water equal to its own weight due to Archimede's principle, which states that the buoyant force is equal to the weight of the displaced fluid.
Question 13:
A student observed that smoke particles in a smoke cell move randomly. State what:
(a) causes this motion; (1 mark)
Smoke particles collide with air particles which are also in continuous random motion.
(b) happens to the motion of the particles if the temperature in the cell is increased. (1 mark)
Motion of the particles increase.
SECTION B (55 marks)
Answer all the questions in this section in the spaces provided.
14. (a)
(i) State the meaning of the term relative density. (1 mark)
Is the ratio of the density of a substance to the density of water at 4 °C.
(ii) State two areas of application of relative density in daily life. (2 marks)
Determine whether an object will float or sink in water.
Calculating the purity of substances like gold. I
(b)A student blew air into a balloon, tied it up and released it into the air. It floated for some time but slowly descended to the ground and settled.
(i) Explain why the balloon settled on the ground. (2 marks)
(i) Explain why the balloon settled on the ground. (2 marks)
It descends as the gas inside it leaks or cools down, reducing its buoyancy.
(ii) State two ways in which the balloon could be made to keep floating in the air. (2 marks)
Fill it with a lighter gas, such as helium
Reduce the weight of the balloon.
(c) A hollow metallic cube of volume 1000 cm³ is submerged in a liquid of density 1100 kgm³. Determine the upthrust acting on it. (take g as 10 Nkg¹) (3 marks)
U = pVg
= 1100 x 0.001 x 10
= 11 N
15. (a)
During an experiment to verify a certain law, a student was provided with some masses, a spring, and a metre rule.
(i) State the law the student wanted to verify. (1 mark)
HOOK'S LAW: For a helical spring or any elastic material, extension is directly proportional to applied force, provided elastic limit is not exceeded.
(ii) State one other apparatus the student needed in order to carry out the experiment. (1 mark)
Stand, boss and clamp.
A pointer.
(iii) Explain how the measurements taken during the experiment are used to verify the law in part (i) above. (3 marks)
(iii) Explain how the measurements taken during the experiment are used to verify the law in part (i) above. (3 marks)
Record the initial length of the spring.
Add different known weights to the spring and measure the extension.
Plot a graph of force (weight) against extension. A straight line through the origin confirms Hook's Law.
(b) A load of 0.04 N causes an extension of 0.4 cm on a certain spring. Determine the load that will cause an extension of 0.6 cm on the same spring. (3 marks)
(b) A load of 0.04 N causes an extension of 0.4 cm on a certain spring. Determine the load that will cause an extension of 0.6 cm on the same spring.
(3 marks)
F = ke
k = F/e = 0.04 N / 0.4m = 10 N/m
F = 10 N/m × 0.006m
= 0.06 N
(c) A student was provided with a piece of wire and asked to make a spring. After coiling the wire on a rod, the spring appeared as shown in Figure 5.
State two ways in which the student can modify the spring to make it stiffer. (2 marks)
Use a thicker wire for the spring.
Reduce the diameter of the coils.
16. (a) Figure 6 shows a setup that may be used to determine acceleration due to gravity.
Describe how the set up may be used to determine the acceleration due to gravity. (4 marks)
Release the mass so it falls freely, pulling the ticker tape through the ticker timer.
The ticker timer will make dots on the tape at regular intervals depending on the frequency of the ticker timer.
Measure the distance between consecutive dots on the ticker tape to determine the displacement at different time intervals.
Plot a graph of displacement against the square of time (t²).
The gradient of the graph gives 1/2 g, where g is the acceleration due to gravity.
b) A stone of mass 0.02 kg tied at the end of a spring is whirled in a vertical circle of radius 1.0 m. Determine the minimum velocity required for the stone to maintain circular motion. (acceleration due to gravity is 10 ms⁻²).
At the top of the circle:
Fc = mg
v = √r x g = √1 x 10
= 3.162 m/s
(c) State two applications of centripetal force. (2 marks)
Keep satellites in orbit.
Maintaining vehicles in curved paths.
17. (a) It is observed that when salt is sprinkled onto the surface of ice at -2 °C, the ice melts. Explain this observation. (2 marks)
Salt lowers the freezing point of water, causing the ice to melt at a lower temperature.
(b) State two factors that determine the pressure exerted by solids.
(2 marks)
Force applied.
Area over which force is applied.
(c) (i) A person mixed 2 kg of hot water at 70 °C with 3 kg of cold water at 22 °C for bathing. Given that the specific heat capacity of water is 4200 Jkg⁻¹K⁻¹, determine the final temperature of the mixture, assuming there was no heat loss.
(3 marks)
Heat loss=Heat gain
mhotwCΔθ = mmixtureCΔθ
The text in the image is an equation and its solution:
2 x 4200 x (80 - T) = 3 x 4200 x (T - 20)
= 44 °C
(ii) State two possible factors that can lead to heat loss in (i).
(2 marks)
Heat loss to the surrounding.
Conduction through the container.
Through evaporation of water.
(d) Some water at 60 °C was heated until it started to boil after time t seconds.
(i) On the axes provided, sketch a graph of temperature against time for the water till it boiled.
(2 marks)
(ii) Explain the shape of the graph in (i). (2 marks) Temperature increased steadily until boiling point, then it remains constant during boiling as heat is used to convert liquid to vapour.
18 (a) Explain why the walls of a dam are thicker at the bottom than at the top. (3 marks) The pressure exerted by water increases with depth, so thicker walls are needed at the bottom to withstand greater pressure.
(b) Figure 7 shows a simple hydraulic lift system.
(i) Given that the areas A1 and A2 are 0.2 m² and 4 m² respectively, determine the maximum load that can be lifted at piston 2, when a force of 200 N is applied at piston 1. (3 marks)
(ii) State two reasons why water is not a suitable liquid for use in this system. (2 marks)
Water is compressible.
Water has high freezing point and low boiling point.
Water corrodes parts of the system.
(c) Figure 8 shows a pair of scissors.
(i) On the diagram, label the load, effort and fulcrum. (1 mark)
(ii) Explain how the velocity ratio of the given pair of scissors may be reduced. (2 marks)
By increasing the distance between the fulcrum and the effort.
(iii) State the reason why it is important to minimize the velocity ratio. (1 mark)
It leads to higher force multiplication.