** **__A2__

Work = force x distance

Energy is the capacity a thing has to do work

Power is the rate of work being done

Power = work / time

The work energy principle:

change in kinetic energy is equal to the net work done

This is derived from the conservation of energy principle.

__University__

These relationships are expressed more mathematically at university:

(*W* is work, *P* is power, *t* is time, *F* is force in vector form, *p* is momentum in vector form, *U* is potential energy, *x* is distance)

From Newton’s laws, momentum and impulse we saw that Newton’s second law states:

We can also write the work equation in terms of potential energy, *U*. This means that the force in the x direction is equal to the negative of the derivative of potential energy with respect to distance in the x direction:

This can be applied in the y and z directions, so the total force is:

The triangle symbol is the del operator, and means that *U* is differentiated with respect to x to give the i component, y to give the j component and z to give the k component of the vector.

Back to Contents: Physics: Mechanics

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