Question

Explain why workdone on a machine is positive and workdone by the machine is negative

Answer 1

W= F S cos theta

If F and S are in same direction work is positive.

If F and S are in opposite direction work is negative . Here theta is 180

cos 180= -1

Hope it helps

Answer 2

A force is said to do positive work if (when applied) the force has a component in the direction of the displacement of the point of application. A force does negative work if the force has a component opposite to the direction of the displacement at the point of application of the force.

hope it helps