## What is Work?

To introduce the definition of work done by a force, we begin with the simple case of motion along a straight line, with the force along the line of motion, Consider a particle moving along a straight line, say, the x-axis, and suppose that a constant force F, directed along the same straight line, acts on the particle. For example, the particle might be a stalled automobile that you are pushing along a road.

**Then the work done by the force F on the particle as it moves some given distance S is defined as the product of the force and the displacement,**

W = F. S =FSCos α

where α is the angle between the force F and the displacement S. Work

is a scalar quantity. The unit of work is

[W] = [F] [S]

In metric system, unit of work is Joule.

[W] = 1 Joule = 1 N.m

In CGS system, unit of work is erg.

Relation between the units of work is

1 Joule = 1 N.m = 10

^{5}D. 10^{2}cm = 10^{7}ergs.