Question

select the correct answer
an athlete is working out in the weight room. he steadily holds 50 kilograms above his head for 10 seconds. which statement is true about this situation?

a. the athlete isn’t doing any work because he doesn’t move the weight

b. the athlete isn’t doing any work because he doesn’t hold the weight long enough

c. the athlete is doing work because he prevents the weight from falling downward

d. the athlete is doing work because 50 kilograms is a significant load to lift

Explanation:

To determine if work is done, we use the physics definition of work: \( W = F \cdot d \), where \( F \) is force and \( d \) is displacement in the direction of the force. In this case, the athlete holds the weight steady, so there is no displacement (\( d = 0 \)).

• Option A: Since work requires displacement, and the weight doesn't move, no work is done. This matches the physics definition.
• Option B: Work doesn't depend on time held, but on displacement. Eliminate B.
• Option C: Preventing fall doesn't involve displacement of the weight, so no work. Eliminate C.
• Option D: The load's size doesn't determine work; displacement is needed. Eliminate D.

Answer:

A. The athlete isn’t doing any work because he doesn’t move the weight