Question

Three porters are carrying luggage on their heads. Identify the nature of work done by the porters against the gravity on the luggage.

Answer 1

Porter 1 is moving down the stairs, the force applied by him is in the upward direction but since he is moving down, the work done will be negative.

Porter 2 is moving in a horizontal direction. The force he applies on the luggage will be in the upward direction, the displacement is in the horizontal direction.
The angle between the force and the displacement in this case is 90° and hence, the work done is zero.

Porter 3 is moving up and the force applied is upward on the luggage. Hence, the work done is positive.