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.

1. Definition of Work in Physics:
– Work is defined as the product of force and displacement in the direction of the force applied.

2. Force Exerted by the Person:
– The person exerts a force against gravity to hold the bundle of hay over his head, countering the weight of the hay.

3. Absence of Displacement:
– Despite exerting a force to hold the bundle, there is no vertical displacement or change in the position of the hay during the 30 minutes.
– The bundle of hay remains stationary and does not move vertically while being held.

4. Work Calculation Criteria:
– For work to be done, there must be a displacement in the direction of the force applied.
– Work is calculated as W = F x d x cos(θ), where F is force, (d) is displacement, and (θ) is the angle between force and displacement.

5. No Displacement, No Work Done:
– In this scenario, although the person exerts a force to counteract gravity, there is no vertical movement or displacement of the hay.
– The absence of vertical displacement means that the force applied by the person does not result in any work being done on the bundle of hay.

6. Explanation of Fatigue:
– The person may feel tired due to muscular effort expended to maintain the position of the hay against gravity for an extended period.
– However, the fatigue is not due to the performance of physical work in the physics sense as there is no displacement in the direction of the force applied.