A heavy suitcase is carried by a porter down a flight of stairs. The work done on the suitcase by the Earth's gravity is
A) zero.
B) positive.
C) negative.
D) unknown; more information is needed to work out the answer.

Question

Quizplus · Accepted Answer

The work done on the suitcase by Earth's gravity is positive because the force of gravity (which acts downward) and the displacement of the suitcase (also downward, as it is carried down the stairs) are in the same direction, resulting in positive work.

A Heavy Suitcase Is Carried by a Porter Down a Flight