Conservation of linear momentum explains that a body or a system of bodies in motion retains its total momentum unless an external force is applied to it. In isolated systems like the Universe, there are no external forces hence momentum is always conserved.
Question and Answer
1. How is a jet plane able to fly in the air?
- The thrust of the jet plane compensates the force of gravity
- The weight of the air is the weight of the plane
- The force of gravity doesn’t act on bodies moving with high speed
- The flow of the air around the wings cause an upward force which compensates for the force of gravity
Answer: (a) The thrust of the jet plane compensates the force of gravity
2. A player catches a ball of mass 150 gm moving at a rate of 20 m/s. If the process of catching is to be completed in 0.1 sec. What is the force exerted by the ball on the hands of the player?
- 3000 N
- 300 N
- 30 N
- 0.3 N
Answer: (c) 30 N
3. When a force acts on a ball of mass 150 g for 0.1 sec, it produces an acceleration of 20 m/s2. What is the value of this impulsive force?
- 0.5 N-s
- 0.1 N-s
- 0.3 N-s
- 1.2 N-s
Answer: (c) 0.3 N-s
4. What is the motion of the rocket based on?
- Linear Momentum
- Kinetic Energy
- Angular Momentum
Answer: (b) Linear Momentum
5. Which of the following is momentum closely related to?
- Kinetic Energy
Answer: (a) Impulse
6. Rocket Engines lift rocket from the earth surface because the hot gas with high velocity
- Push against the air
- Push against the earth
- Heat up the air which lifts the rocket
- React against the rocket and push it up
Answer: (d) React against the rocket and push it up
7. A bullet of mass 5 gm is fired from a gun of mass 5 kg. What is the velocity of the muzzle if the recoil velocity is 500 m/s.
- 500 m/s
- 5 m/s
- 50 m/s
- 0.5 m/s
Answer: (d) 0.5 m/s
8. A rope of length 5 m is kept on a frictionless surface and a force of 5 N is applied to one of its ends. What is the tension in the rope at 1 m from this end?
- 1 N
- 4 N
- 3 N
- 5 N
Answer: (b) 4 N
9. A wagon weighing 1000 kg moves 50 km/h on smooth rails. Later, a mass of 250 kg is placed in the wagon. What is the velocity with which it moves?
- 20 km/hr
- 50 km/hr
- 40 km/hr
- 2.5 km/hr
Answer: (c) 40 km/hr
10. An iron ball having a mass of 100 g with a velocity of 10 m/s collides with the wall at an angle of 300 and rebounds with the same angle. If the period of contact between the wall and the ball is 0.1 second. What is the force experienced by the ball?
- 0.1 N
- 1 N
- 10 N
- 100 N
Answer: (c) 10 N
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