Question

which one of these forces is doing negative work

Answer 1

what are the options my friend

Answer 2

a) The direction in which the force of gravity works is downward direction.

b) The force of gravity is doing positive work, because, the force pulls down and the value of theta is 0 . So, cos theta=cos 0 degree=1. Thus, work done by force of gravity is positive.

c) The student does a negative work, because, the angle between lifting the body and force of gravity is 180 degree. Thus, cos theta=cos 180 degree= -1.

Hence, the work done by the boy is negative.