Two springs of spring constants k and 3k are stretched separately by the same force. The ratio of potential energy stored in them respectively, will be: 

1.	3: 1	2.	9: 1
3.	1: 3	4.	1: 9

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 the gravitational force on block \(A\) during the first \(2\) s after the blocks are released? (assume the pulley is light)

1. \( 240 ~\text J\)
2. \( 200 ~\text J\)
3. \(120 ~\text J\)
4. \( 24 ~\text J\)

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 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: