A pulley on a horizontal plane drags a mass M with a force anti-parallel to its displacement. The work done in pulling the mass M is as follows:

A force is said to do work (W) when the force acting on it causes an object to displace.

It is given mathematically by:

w=Fd cos θ

Given: The pull force F is applied to the displacement of the mass on the plane in an antiparallel direction.

According to the diagram, the displacement and pulling force vectors will be antiparallel to each other because the angle between them is 180 degrees.

θ=180^o

Cos180^o=-1

As a result of using equation 1, the work done in pulling the mass M will be negative because the magnitude of the force and displacement vector cannot be negative.