Q.1. An explosion breaks a rock into three parts in a horizontal plane. Two of them go off at right angles to each other. The first part of mass 1 kg moves with a speed of 12 m/s and the second part of mass 2 kg moves with 8 m/s speed. If the third part flies off with 4 m/s speed, then its mass is

(a) 3 kg

(b) 5 kg

(c) 7 kg

(d) 12 kg

Answer: (b)

Q.2. A rigid ball of mass m strikes a rigid wall at 60^{0} and gets reflected without loss of speed as shown in the figure. The value of the impulse imparted by the wall on the ball will be

**(a) mv**

(b) 2mv

(c) mv/2

(d) mv/3

Answer: (a)

**Q.3. How is a jet plane able to fly in the air?**

(a) The thrust of the jet plane compensates the force of gravity

(b) The weight of the air is the weight of the plane

(c) The force of gravity doesn’t act on bodies moving with high speed

(d) 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

**Q.4. 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?**

(a) 3000 N

(b) 300 N

(c) 30 N

(d) 0.3 N

Answer: (c) 30 N

**Q.5. When a force acts on a ball of mass 150 g for 0.1 sec, it produces an acceleration of 20 m/s ^{2}. What is the value of this impulsive force?**

(a) 0.5 N-s

(b) 0.1 N-s

(c) 0.3 N-s

(d) 1.2 N-s

Answer: (c) 0.3 N-s

Q.6. A particle of mass m moving with velocity v strikes a stationary particle of mass 2m and sticks to it. The speed of the system will be

(a) v/2

(b) 2v

(c) v/3

(d) 3v

Answer: (c)

**Q.7. What is the motion of the rocket based on?**

(a) Mass

(b) Linear Momentum

(c) Kinetic Energy

(d) Angular Momentum

Answer: (b) Linear Momentum

Q.8. A body, whose momentum is constant, must have constant

(a) Force

(b) Velocity

(c) Acceleration

(d) All of these

Answer: (b)

**Q.9. Which of the following is momentum closely related to?**

(a) Impulse

(b) Power

(c) Force

(d) Kinetic Energy

Answer: (a) Impulse

**Q.10. 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.**

(a) 500 m/s

(b) 5 m/s

(c) 50 m/s

(d) 0.5 m/s

Answer: (d) 0.5 m/s

**Q.11. Rocket Engines lift rocket from the earth surface because the hot gas with high velocity**

(a) Push against the air

(b) Push against the earth

(c) Heat up the air which lifts the rocket

(d) React against the rocket and push it up

Answer: (d) React against the rocket and push it up

**Q.12. 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?**

(a) 1 N

(b) 4 N

(c) 3 N

(d) 5 N

Answer: (b) 4 N

Q.13. The momentum of a system is conserved [CPMT 1982]

(a) Always

(b) Never**(c) In the absence of an external force on the system**

(d) None of the above

Answer: (c)

**Q.14. 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?**

(a) 20 km/hr

(b) 50 km/hr

(c) 40 km/hr

(d) 2.5 km/hr

Answer: (c) 40 km/hr

**Q.15. 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?**

(a) 0.1 N

(b) 1 N

(c) 10 N

(d) 100 N

Answer: (c) 10 N

Q.16. A force of 50 dynes is acted on a body of mass 5 g which is at rest for an interval of 3 seconds, then impulse is

(a) 0.15 x 10^{-3} Ns

(b) 0.98 x 10^{-3} Ns

(c) 1.5 x 10^{-3} Ns

(d) 2.5 x 10^{-3} Ns

Answer: (c)