top of page


The rate that energy is transferred or work is done.

Anchor 1

1. Mechanical Power

The rate of energy transfer is sometimes more useful to consider than the total energy transferred. Not only is P = E/t but it can also be written as P = Fv.

Anchor 2

2. Efficiency

Although we often assume 100% of the energy is transferred from one form to another this is not always the case. When energy is lost from the system (perhaps as thermal energy) then its efficiency decreases.

Anchor 3

3. Power

This is how we define power, as well as a couple of simple examples using the formula P=W/t.

How to Derive:

(Worksheets and solutions)

bottom of page