In order to find an object’s velocity, we can integrate the acceleration over time. We can integrate again (the velocity) to find an object’s position.

If we do the same thing with energy, we find that the change in energy with respect to time is called Power. But the change in energy is also referred to the as Work, so we get two definitions for Power.

• Power [j/s or w] = Change in Energy over time. P=dE/dt

Power is measured in Watts where one Watt equals one Joule/second.

But what do we mean when we say that someone’s kick is powerful? We need a few more concepts to explain what happens when someone strikes another person. There are two critical things that happen- a transfer of momentum and a transfer and dissipation of energy.