Question

When a stone tied to a string is whirled in a circle, the work done on it by the string is:

• A. Positive
• B. Negative
• C. Zero
• D. Undefined

Answer 1

The correct option is C Zero

Work done by the centripetal force is zero. As centripetal force is perpendicular to the direction of motion, the work done by it will be 0. Definition of Work Done = $F.Scos\Theta$. Here in this case force is always directed perpendicular to the direction of the motion so $\Theta$ is 90. Therefore, work done is zero.