a person pulls a cart at 4.5 m/s and pushes it with a force 20 N [east]. What is the power exerted by the person.

Question

anonymous · Answer

A simple derivation.  Power is the amount of energy spent per unit time (or teh work done per unit time).  that is $$P=\frac{E}{t}$$  But we know that the work done in pushing an object with a force F, over a distance d is (which is the energy put into a system) is given by $$E=Fd$$Hence$$P=\frac{Fd}{t}=F\times \frac{d}{t}$$But we know that the velocity is $v=d/t$, and hence we get that $$P=F\times v$$.

Form this equation plug in the numbers and you can get $P=20\times 4.5=90$ Watts.