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# Form 3 Physics Newton's laws of motion questions and answers

This online session contains Form 3 Physics Newton's Laws of Motion questions and answers. The questions are well explained with video solutions.

Lessons (**24**) * SHARE*

- 1.
State Newton’s first law of motion.

2m 6s - 2.
A trolley is moving at constant speed in friction compensated track. Some plasticine is dropped on the trolley and sticks on it. State
with a reason what is observed about the motion of the trolley.

2m 14s - 3.
A gun is fired vertically upwards from the top of an open truck moving horizontally at a uniform velocity of 50 ms-1. The bullet achieves a maximum
height of 45m.
(i) State with reason whether or not the bullet will land on the truck.
(ii) Calculate the distance covered by the truck just before the bullet reaches the level from which it was fired. (Use g=10 #ms^-2#).

7m 26s - 4.
An industrial trolley of mass 20kg carrying a mass of 50kg is acted on by a constant force. The trolley moves along a horizontal smooth
surface with an acceleration of #0.5 ms^-2#. Determine the acceleration of the trolley after the mass falls off.

2m 42s - 5.
A body initially resting on horizontal frictionless surface is accelerated by a constant force. It passes over a small region where it experiences a force of
friction equal to the accelerating force before returning to the frictionless horizontal surface. On the axis, provided, sketch the velocity – time graph for the motion of the body.

5m 5s - 6.
(a) Two identical spherical steel balls are released from the top of two tall jars containing liquids L1 and L2 respectively.
Figure 3 shows the velocity – time graph of the motion of the balls.
Explain the nature of the curves and state why they are different.
(b) In an experiment to determine the proportionality constant, µ between two wooden surfaces sliding on each other, a block of mass

12m 55s - 7.
Figure 15 shows a tall jar containing two fluids A and B. the viscosity of A is higher than that of B. a solid sphere is released at the top of the
jar and falls through the fluids. On the axis provided, sketch the velocity – time graph for the motion of the spheres through the fluids.

5m 55s - 8.
(a) (i) State one of the Newton’s law of motion.
(ii) A body resting on a horizontal surface is given an initial velocity V so that it slides on the surface for some distance before coming
to a stop. Table 1 shows the distance d moved by the body of various values of V.
Given that #V^2# = 20µd where µ is a constant for the surface, plot an appropriate graph and use it to determine µ.

10m 44s - 9.
A high jumper usually lands on thick soft mattress.
Explain how the mattress helps in reducing the force of impact.

2m 53s - 10.
A resultant force F acts on a body of mass m causing an acceleration #a_1# on the body.
When the same force acts on a body of mass 2m, it causes an acceleration #a_2#. Express #a_2# in terms of #a_1#.

2m 46s - 11.
A trolley is moving at a uniform speed along a track. A piece of plasticine is dropped on the trolley and sticks on it. Explain why the trolley slows down.

2m 22s - 12.
Figure 14 shows the velocity– time graph for a small metal sphere falling through a viscous fluid.
On the axis provided, sketch the graph of momentum against time for the same mass.

2m 41s - 13.
A footballer kicks a ball of mass 0.6 kg initially at rest using a force of 720N. if the foot was in contact with the ball for 0.1 seconds, what was the takeoff speed of the ball?

2m 46s - 14.
(a) State newton’s first law of motion.
(b) A wooden block resting on a horizontal bench is given an initial velocity, u, so that it slides on the bench surface for a distance, n, before
coming to stop. The values of d were measured and recorded for various values of initial velocity.
Figure 10 shows the graph of #u^2# against d.
(i) Determine the slope, s, of the graph.
(ii) Given that #u^2#= 20k

11m 54s - 15.
State Newton’s second law of motion.

1m 23s - 16.
A cart of mass 30kg is pushed along a horizontal path by a horizontal force of 8N and moves with a constant velocity. The force is then increased to 14N.
Determine:
(a) The resistance to the motion of the cart
(b) The acceleration of the cart.

3m 0s - 17.
(a) Figure 12 shows a lorry towing a trailer using a rope.
The lorry exerts a force N on the trailer and the trailer exerts an equal but opposite force M on the lorry. The frictional force between the trailer and the road is F. Explain how the forces N, M and F enable the trailer to move.
(b) Figure 13 shows a frictionless trolley of mass 2kg moving with uniform velocity towards a wall. At the

5m 41s - 18.
A student pulls a block of wood along a horizontal surface by applying a constant force. State the reason why the block moves at a constant velocity.

2m 22s - 19.
Figure 9 shows a trolley on a smooth surface being pulled by a constant force F.
(i) On the axis provided, sketch the velocity –time graph for the motion of the trolley.
(ii) A parachute falling through the air attains terminal velocity after a short time. State the reason why it attains terminal velocity.

3m 9s - 20.
A horizontal force of 12N is applied on a wooden block of mass 2kg placed on a horizontal surface. It causes the block to accelerate at 5
#ms^-2#. Determine the frictional force between the block and the surface.

2m 3s - 21.
Using the definition of impulsive force, show that F=ma.

2m 5s - 22.
(a) A wooden block resting on horizontal bench is given an initial velocity u so that it slides on the bench for a distance X before it stops. Various
values of X are measured for different values of the initial velocity. Figure 9 shows a graph of #u^2# against x.
(i) Determine the slope S of the graph.
(ii) Determine the value of k, given that #u^2# = 20kd where k is a frictional constant for the

7m 42s - 23.
Two boxes E and F of masses 2.0kg and 4.0kg respectively are dragged along a frictionless surface using identical forces. State with a reason which box
moves with a higher velocity.

2m 16s - 24.
Figure 8 shows the graph of velocity against time for a small steel ball falling in a viscous liquid.
(i) Describe the motion of the steel ball as represented by part OA.
(ii) Explain why the velocity between A and B is constant.

5m 53s