1. A body of mass 10 kg is initially at a height of 20 m above the ground. It falls to a height of 5 m above the ground. Its potential energy in the new position is

2. A man of 60 kg weight is standing at rest on a platform. He jumps up vertically a distance of 1 m and the platform at the same instant moves horizontally forward with the result that the man lands 1 meter behind the point on the platfrom from where the took the jump the total work done by the man at the instant he lands is

3. A marble moving with some velocity collides perfectly elastically head-on with another marble at rest having mass 1.5 times the mass of the colliding marble. The percentage of kinetic energy by the colliding marble after the collision is

4. A body of mass 100 kg falls from a height of 10 m. Its increase in kinetic energy is

5. An isolated particle of mass m is moving in a horizontal plane (x-y), along the x-axis, at a certain height above the ground. It suddenly explodes into two fragments of masses m/4 and 3m/4 . An instant later, the smaller fragment is at y = + 15 cm. The larger fragment at this instant is at

6. A uniform chain of length 2 m is kept on a table such that a length of 60 cm hangs freely from the edge of the table. The total mass of the chain is 4 kg. What is the work done in pulling the entire chain on the table?

7. A body of mass 20 kg is initially at a height of 3 m above the ground. It is lifted to a height of 2 m from that position. Its increase in potential energy is

8. A body of mass 10 kg is moved parallel to the ground, through a distance of 2 m. The work done against gravitational force is

9. A ball is dropped from a height of 1 m. If the coeffcient of restitution between the surface and ball is 0.6, the ball rebounds to a height of

10. An electric heater of rating 1000 W is used for 5 hrs per day for 20 days. The electrical energy utilised is