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:

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:

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 head-on elastically with another identical body at rest. The percentage loss in kinetic energy of the first body will be:

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