Laws of Motion Quiz - ICSE Class 9 Physics

Free practice quiz: Laws of Motion (ICSE Class 9 Physics). 51 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This ICSE Class 9 Physics practice quiz has 51 multiple-choice questions on Laws of Motion, and 51 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. A body of mass $m$ is moving with velocity $v$. If its velocity is doubled, what will be its new kinetic energy?

   1. Half of the original kinetic energy
   2. The same as the original kinetic energy
   3. Twice the original kinetic energy
   4. Four times the original kinetic energy
   Show answer

   Answer: D. Four times the original kinetic energy

   The kinetic energy of a body is given by the formula $KE = \frac{1}{2}mv^2$. If the velocity is doubled, the new velocity is $2v$. The new kinetic energy will be $KE_{new} = \frac{1}{2}m(2v)^2 = \frac{1}{2}m(4v^2) = 4 \times \frac{1}{2}mv^2 = 4 \times KE$. Therefore, the new kinetic energy is four times the original kinetic energy.

2. A body of mass 10 kg is moving with a velocity of 5 m/s. If an additional force of 20 N is applied in the direction of motion for 4 seconds, what will be the final velocity?

   1. 7 m/s
   2. 9 m/s
   3. 11 m/s
   4. 13 m/s
   Show answer

   Answer: D. 13 m/s

   First, let's find the change in momentum due to the applied force. Impulse = Force $\times$ time $= 20 \text{ N} \times 4 \text{ s} = 80$ N-s. The change in momentum is also equal to $m \times \Delta v$. So, $80 = 10 \text{ kg} \times \Delta v$. This gives $\Delta v = \frac{80}{10} = 8$ m/s. The initial velocity is 5 m/s. Since the force is applied in the direction of motion, the velocity will increase. The final velocity $v_{final} = v_{initial} + \Delta v = 5 \text{ m/s} + 8 \text{ m/s} = 13$ m/s.

3. A force of 100 N acts on a body of mass 50 kg. If the body starts from rest, what is its velocity after 5 seconds?

   1. 10 m/s
   2. 20 m/s
   3. 5 m/s
   4. 2.5 m/s
   Show answer

   Answer: A. 10 m/s

   First, find the acceleration using Newton's second law, $F = ma$. $a = \frac{F}{m} = \frac{100 \text{ N}}{50 \text{ kg}} = 2$ m/s$^2$. Since the body starts from rest ($u=0$), its velocity after time $t$ is given by $v = u + at$. $v = 0 + (2 \text{ m/s}^2 \times 5 \text{ s}) = 10$ m/s.

4. A body of mass 5 kg is moving with a velocity of 4 m/s. If a force of 10 N is applied for 3 seconds, what is the new momentum?

   1. 20 kg-m/s
   2. 50 kg-m/s
   3. 60 kg-m/s
   4. 80 kg-m/s
   Show answer

   Answer: B. 50 kg-m/s

   The initial momentum of the body is $p_{initial} = mv = 5 \text{ kg} \times 4 \text{ m/s} = 20$ kg-m/s. The impulse applied by the force is $I = F imes t = 10 \text{ N} \times 3 \text{ s} = 30$ N-s. The change in momentum is equal to the impulse, so $\Delta p = 30$ kg-m/s. The new momentum is $p_{new} = p_{initial} + \Delta p = 20 \text{ kg-m/s} + 30 \text{ kg-m/s} = 50$ kg-m/s.

5. A car of mass 1200 kg is moving with a velocity of 15 m/s. If the brakes are applied and the car stops in 5 seconds, what is the force applied by the brakes?

   1. 3600 N
   2. -3600 N
   3. 7200 N
   4. -7200 N
   Show answer

   Answer: B. -3600 N

   First, calculate the initial momentum $p_{initial} = mv = 1200 \text{ kg} imes 15 \text{ m/s} = 18000$ kg-m/s. The final momentum $p_{final} = mv = 1200 \text{ kg} imes 0 \text{ m/s} = 0$ kg-m/s (since the car stops). The impulse is the change in momentum: $I = p_{final} - p_{initial} = 0 - 18000 = -18000$ kg-m/s. Impulse is also equal to Force $\times$ time ($I = Ft$). So, $-18000 \text{ kg-m/s} = F \times 5 \text{ s}$. The force $F = \frac{-18000 \text{ kg-m/s}}{5 \text{ s}} = -3600$ N. The negative sign indicates that the force is acting in the opposite direction to the initial motion.

More questions in this quiz

Answers and explanations are in the full quiz.

1. According to Newton's third law of motion, for every action, there is an...
2. A force of 10 N is applied to a body of mass 5 kg. What is the acceleration produced in the body?
3. Which of the following quantities is a vector quantity?
4. A car is moving at a constant velocity. What is the net force acting on the car?
5. Inertia is the property of a body by which it tends to...
6. When a bus suddenly starts moving, the passengers tend to fall backward. This is an example of:
7. What is the unit of impulse in the SI system?
8. Which of the following is an example of a conservative force?
9. If the momentum of a body is doubled, its kinetic energy will be:
10. What is the SI unit of force?
11. A body is initially at rest. What is its momentum?
12. Which law of motion states that the rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction in which the force is applied?
13. A car of mass 1000 kg is moving at a speed of 20 m/s. What is its kinetic energy?
14. When a person jumps out of a moving train, they fall forward. This is because:
15. A constant force acts on a body of mass 2 kg. If the force causes an acceleration of 10 m/s$^2$, what is the magnitude of the force?
16. Which of the following is a consequence of Newton's third law of motion?
17. A cannon fires a ball. In which direction does the cannon recoil?
18. The product of mass and velocity of a body is called:
19. Which of the following statements about inertia is INCORRECT?
20. A boat is rowed at a constant speed. Which of the following describes the forces acting on the boat?
21. Which principle states that in the absence of external forces, the total momentum of a system remains constant?
22. A body of mass $m$ is projected upwards with velocity $v$. What is its momentum at the highest point of its trajectory?
23. When a carpet is beaten with a stick, dust particles fly off it. This is an application of:
24. A force of 20 N is applied to a block of mass 10 kg resting on a smooth horizontal surface. What is the acceleration of the block?
25. If the momentum of a body increases by 50%, what is the percentage increase in its kinetic energy?
26. A person is pushing a heavy box across a floor. If the box is moving at a constant velocity, it implies that:
27. What is the term for the property of a body to resist any change in its state of rest or of uniform motion?
28. Which of the following is an example of an action-reaction pair according to Newton's third law?
29. A body is moving with constant momentum. This means:
30. When a fire hose sprays water, the person holding the hose experiences a backward push. This is due to:
31. What is the relationship between force, mass, and acceleration as described by Newton's second law?
32. A bullet is fired from a gun. The gun recoils due to:
33. If the speed of a body is doubled, its momentum will be:
34. When you push against a wall, the wall pushes back on you with an equal and opposite force. This illustrates:
35. A body is acted upon by a net force of 10 N. If its mass is 2 kg, what is its acceleration?
36. Which of the following quantities is conserved in a collision between two objects, provided there are no external forces acting on the system?
37. Which statement best describes the relationship between mass and inertia?
38. A rocket propels itself forward by expelling hot gases downwards. This is an example of:
39. If the velocity of a body is tripled, its kinetic energy will be multiplied by a factor of:
40. A car is moving at a constant velocity of 10 m/s. If the driver applies brakes, causing a deceleration of 2 m/s$^2$, what is the distance covered by the car before it stops?
41. Which of the following is a scalar quantity?
42. A body is in equilibrium. This means that:
43. When a person stops pedaling a bicycle, it eventually slows down and stops. This is primarily due to:
44. A constant force of 50 N is applied to a mass of 10 kg for 2 seconds. What is the change in velocity?
45. The product of force and the time for which it acts is equal to:
46. Which of the following correctly states Newton's first law of motion?

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