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

On doubling the velocity of a moving body, the quantity which gets double is:

1. acceleration
2. momentum
3. kinetic energy 
4. weight

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