Question

A pendulum is released from one of its extreme positions. What will be its velocity when it passes the mean position and when it reaches the other extreme position?

Answer 1

The bob of a simple pendulum is attached to a string which pulls the bob along its length.

When the bob is at the extreme position B, the string pulls it along (BO) and the Earth pulls the bob vertically downwards. Since the string and the Earth are pulling the bob in the opposite directions, the two forces cannot balance each other. As a result, the bob moves along the dotted line as shown in the above figure. The speed of the bob increases as it approaches the mean position A and continues to move till it reaches C. At C the speed becomes zero and due to the unbalanced force, the bob moves towards the mean position. The speed of the bob is maximum at the mean position and is zero at the extreme positions.