Anyone pushing a heavy crate across a storeroom floor would be justified in thinking that it was hard work. This is a common concept of work, i.e. making an effort to move an object, and it is reflected in the following definition of mechanical work.

When an object moves under the action of a constant force F, the amount of work done by the force is given by :

the component of F in the direction of motion x distance moved.

 

 

 

 

 

 

 

If the force is measured in newtons and the distance in metres, the work done is measured in joules (J).

For example, if a force of 12 N acts on a body and moves it a distance of 3 m in the direction of the force, the amount of work done by the force is 36 J.

Note that work is done only if the force succeeds in moving the object. A force applied to an object that remains at rest, does not do any work.

When several forces act on one body, the work done by each force can be found independently of the others.