A simple pendulum while oscillating rises to a maximum vertical height of 7 cm from its rest position where it reaches its extreme position on one side. The mass of the bob of simple pendulum is 400 g and g = 10 m/s². The total energy of the simple pendulum at any instant while oscillating is:

1. 0.28 J
2. 2.8 J
3. 28 J 
4. 28000 J

Assertion (A): When a hammer is made to fall on a nail fixed upright on a wooden piece, the nail begins to penetrate the wood.

Reason (R): As the hammer starts falling, its kinetic energy begins to change into potential energy.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true and R is not the correct explanation of A.
3. assertion is false but reason is true.
4. assertion is true but reason is false.

A body falls freely under gravity from rest. Name the kind of energy it will possess

(a) At the point from where it falls.

(b) While falling

(c) On reaching the ground.

State the Principle of conservation of energy.