Question

A pendulum is oscillating on either side of its rest position. Name the kind of energy it possess at:

(i) the rest position.

(ii) the extreme position on either side.

(iii) midway between the rest position and the extreme position.

Answer 1

1. When the bob swings from A to B, the kinetic energy decreases and the potential energy becomes maximum at B where it is momentarily at rest.
2. From B to A, the potential energy again changes into the kinetic energy and the process gets repeated again and again.
3. Thus, while swinging the bob has only the potential energy at the extreme position B or C and only kinetic energy at resting position A.
4. At an intermediate position (between A and B or between A and C) the bob has both the kinetic energy and potential energy.
5. The sum of both the energies (i.e the total mechanical energy) remains constant throughout the swing.

(i) If A pendulum is oscillating on either side of its rest position then at rest position it would be having Kinetic energy.

(ii) At the extreme position on either side potential energy is maximum and kinetic energy is zero.

(iii) Midway between the rest and extreme the bob has both the kinetic energy and potential energy.