When standing still with a heavy load on your head, you expend energy and get tired. Why is zero work done on

Question

When standing still with a heavy load on your head, you expend energy and get tired. Why is zero work done on the load?

Examoogle · Accepted Answer

The correct answer is Option C: There is no displacement of the load.. In physics, work is defined as the product of the component of the force in the direction of displacement and the magnitude of the displacement. Since the load on the person's head does not undergo any displacement ($s = 0$), the physical work done on the load is zero, regardless of the effort exerted.

Step-by-Step Solution & Concepts:
In physics, work is defined as the product of the component of the force in the direction of displacement and the magnitude of the displacement. Since the load on the person's head does not undergo any displacement ($s = 0$), the physical work done on the load is zero, regardless of the effort exerted.

Working Principle: The mechanical work $W$ is calculated using the formula $W = F \cdot s \cdot \cos(	heta)$, where $F$ is the applied force, $s$ is the displacement, and $	heta$ is the angle between them. When a person stands still, the displacement $s$ is zero. Consequently, even if a significant muscular force is applied to balance gravity, the lack of spatial movement results in $W = 0$ Joules.

Key Formulas: $W = Fs \cos(	heta)$ — Work done formula where $W$ is work, $F$ is force, $s$ is displacement, and $	heta$ is the angle.; $s = 0$ — Condition for zero mechanical work when displacement is absent.

Key Points: Work is a dot product of Force and Displacement vectors.; Biological energy expenditure is not equivalent to mechanical work done on an external object.; The body tires due to muscle contraction and tension, which consumes metabolic energy internally without producing external displacement.

Applications: Holding an object at a constant height.; Pushing against a stationary wall.

Additional Info: Work done by gravity on the load is also zero because it is not moving.. Option A is irrelevant because even with a vertical force, displacement is required for work.. Option B is incorrect because time is a factor in power, not the definition of work.. Option D is incorrect because force is indeed applied; it is equal and opposite to the gravitational force $F = mg$.

Answer: C is correct — Scientific work requires both force and displacement, and since the load remains stationary, no displacement occurs, resulting in zero work.

Exam Tip: In competitive exams, always distinguish between 'biological work' (fatigue, calorie burn) and 'physical work' (force applied over distance). If displacement is zero, physical work is always zero.

Examoogle · Answer

Option A: The force applied is vertical.

Examoogle · Answer

Option B: The time elapsed is irrelevant.

Examoogle · Answer

Option D: Force is not being applied.

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Discussion (0)

Correct Answer

Solve 10,000+ More Questions with AI Tutor

Related Questions

Discussion (0)