Power measures howquickly work gets done. For example, a force of 100J of work in 20 seconds is being done at a rate of 100J/20s = 5J/s. This is the power (P), and from sample calculation above the units are obviously J/s. This is defined as the watt, W, which should not be confused with the W which defines work.

Power = work/time = W/t

The faster work gets done, the greater the power. If there is constant v and force is parallel to path, then P = Fv

Energy is the ability to do work. Moving objects inherently have energy because they can crash into something and exert a force over a distance. Kinetic energy is this energy of motion.



KE = .5mv2

This assumes the initial speed of the object is 0. If it were not, then W = KEfinal - KEinitial.Wtotal = ΔKE.


Potential energy is energy of an object due to position. There is gravitational, electrical, and elastic potential energy. Potential energy is placed on position in a gravitational field. ΔPEgrav=-Wby Fgrav=mgh. If the brick had fallen, it would have been -mgh.

PE = -mgh

Gravity is a conservative force.