question_answer 25)

A person holds a bundle of hay over his head for 30 minutes and gets tired. Has he done some work or not? Justify your answer.

Answer:

The person holding a bundle of hay on his head gets tired as he experiences muscular fatigue. This fatigue is due to conversion of chemical energy into thermal energy by the muscular effort. The person has done no work as his effort causes no displacement of the bundle over his head, i.e., S = 0.