Mark the correct statement(s):
1. Internal forces cannot increase the kinetic energy of a system.
2. Internal forces may increase the kinetic energy of a system.
3. Work done by kinetic friction is always negative.
4. Both (2) & (3)
A bullet fired towards a wall reduces its kinetic energy by half after the penetration of 6 cm. The further penetration of the bullet into the wall is:
1. 2 cm
2. 1 cm
3. 6 cm
4. 3 cm
A body having an initial kinetic energy 2 J collides with an identical body at rest. The maximum loss of kinetic energy in the collision will be:
1.  2 J  2.  Zero 
3.  1 J  4.  1.5 J 
What is the work done by gravity on block A in 2 seconds after the blocks are released? (Pulley is light)
1. 240 J
2. 200 J
3. 120 J
4. 24 J
A weight 'mg' is suspended from a spring. The energy stored in the spring is U. The elongation in the spring is:
1. $\frac{2\mathrm{U}}{\mathrm{mg}}$
2. $\frac{\mathrm{U}}{\mathrm{mg}}$
3. $\frac{\sqrt{2}\mathrm{U}}{\mathrm{mg}}$
4. $\frac{\mathrm{U}}{\sqrt{2}\mathrm{mg}}$
The energy required to accelerate a car from rest to 30 m/s is E. The energy required to accelerate the car from 30 m/s to 60 m/s will be:
1.  E  2.  2E 
3.  3E  4.  4E 
The speed of a particle moving in a circular path decreases with time. The instantaneous power due to the force acting on it will be:
1. Positive
2. Negative
3. Zero
4. Maybe positive or negative
A body of mass m moving with speed v collides headon elastically with another identical body at rest. The percentage loss in kinetic energy of the first body will be:
1.  0%  2.  25% 
3.  50%  4.  100% 
A body is obliquely projected from the horizontal ground. The magnitude of gravity's power delivered during its motion from the ground to the topmost point is:
1.  Constant

2.  Increases continuously

3.  Decreases continuously

4.  May increase or decrease depending on the angle of projection 
In the given figure, a man pulls the mass m with the help of a rope. Work done by the man against gravity when mass is lifted by 0.5 m is: (g = 10 $\mathrm{m}/{\mathrm{s}}^{2}$)
1. 50 J
2. 100 J
3. 25 J
4. Zero