A body of mass 1 kg is thrown upwards with a velocity of $20$ ${\mathrm{ms}}^{-1}.$ It momentarily comes to rest after attaining a height of 18 m. How much energy is lost due to air friction? $\left(\mathrm{g}=10\right)$ ${\mathrm{ms}}^{-2}$

1. 20 J

2. 30 J

3. 40 J

4. 10 J

When a body moves non-uniformly on a circular path,

1. no work is done by the tangential force.

2. no work is done by the centripetal force.

3. work done by the tangential force is always positive.

4. work done by the centripetal force is negative.

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: 

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