A body of mass 10 kg is moving with a velocity of 20 m/s. The mass of the body is doubled and velocity is halved. Its initial kinetic energy is:

1. 200 J
2. 4000 J
3. 2000 J
4. 1000 J

The kinetic energy K and momentum p are related as:

1. $p = \sqrt{2K}$

2. $p = \sqrt{2gK}$

3. K = $\dfrac{p^2}{2m}$

4. $K = \sqrt{2mp}$

In a photoelectric cell, the change in energy is from:

1. electrical to mechanical
2. light energy to electrical energy
3. electrical energy to light energy
4. chemical energy to light energy

In a petrol vehicle while in motion, the change in energy is from

1. kinetic energy to potential energy
2. chemical energy to kinetic energy
3. potential energy to kinetic energy 
4. chemical energy to potential energy