Question

The hanging bob of a simple pendulum is displaced to one extreme position B and then released. it swings towards centre position A and then to the other extreme position C. In which position does the bob have:
(i) maximum potential energy?
(ii) maximum kinetic energy?
​Give reasons for your answer.

Answer 1

A hanging bob swings around its mean position from one extreme to another extreme position.

(i) The bob has the maximum potential energy at the extreme positions. In the given case, the bob will have maximum potential energy at B and C positions. Because the velocity of the bob becomes zero at the extreme positions, that's why at extremes whole of the energy becomes potential energy.

(ii) At the mean position, the velocity of the bob is maximum as all of the potential energy gets converted into kinetic energy. Hence, at the mean position A, the bob will have the maximum kinetic energy.