Question

Which statements describe a situation in which work is being done? Check all that apply.

A box is carried up a flight of stairs by a mover.
A box sits on a table waiting to be moved.
Wind blows against a steel table anchored to the ground.
Wind blows a pool chair across the yard.
A weightlifter lifts a barbell off the ground.
A weightlifter holds a barbell above his head.

Answer 1

Work in physics requires a force and a displacement in the direction of that force (W = F · d). Applying that:

- A box is carried up a flight of stairs by a mover. — Yes. (Force upward and displacement upward → work done by the mover.)
- A box sits on a table waiting to be moved. — No. (No displacement → no work.)
- Wind blows against a steel table anchored to the ground. — No (on the table). (Force present but no displacement of the table → no work done on the table.)
- Wind blows a pool chair across the yard. — Yes. (Force and displacement in the same direction → work done by the wind.)
- A weightlifter lifts a barbell off the ground. — Yes. (Force upward and displacement upward → work done by the lifter.)
- A weightlifter holds a barbell above his head. — No (mechanical work = 0). (No displacement, so no mechanical work, though the lifter expends metabolic energy.)