Question 1: If two people each carry a weight of 50N up the same hill, which one does more work?
Question 2: What if one of them does it in 1 hour and the other takes 2 hours?
The answer to both of the questions above is that they both do the same amount of work. They both carry the same mass, m through the same height, h so both do
Work done = mgh
In the second question, however, the first person completes the work more quickly. They did more work per second. We say that they were more powerful.
Power is defined as the rate at which you do work.
Units: W, watts. 1 watt = 1 joule per second (= 1 Js-1)
The equation is:
Power = Work Done / Time Taken
Another useful equation can be derived from this. Notice that:
Work done, W = force x displacement =Fs
So, power = or
And, = v
So P =Fv
So Power = Force x velocity; remembering that the force and velocity must be in the same direction.