Question

Imagine lowering a heavy box to the floor. Under what circumstances is the work done on the box by gravity negative?

a. the work done on the box by gravity is always negative in this situation.

b. the work done on the box by gravity is negative while the box is accelerating downward.

c. the work done on the box by gravity is never negative in this situation.

Answer 1

Work done is negative when the force and displacement are in opposite direction.

We know that force of gravity always acts in down direction. hence the force of gravity on the box being lowered is in down direction.

The box is being lowered, hence the displacement of the box is also in down direction.

Clearly, both Force of gravity and displacement are in same direction. hence the work done on the box by gravity can not be negative .

c. the work done on the box by gravity is never negative in this situation.