# The work done by a boy pulling a snow sled up a hill is 425 J. What is the power expended by the boy if he pulls on the sled for 10.5 s?

Dec 8, 2017

$40.5 \text{ watts}$

#### Explanation:

Power is simply work done over time. The formal, calculus based definition is:

$P = \frac{\mathrm{dW}}{\mathrm{dt}}$

However, in more simple applications, you can just write this as:

$P = \frac{W}{t}$

You're given work, and you're given time, so we just plug in & solve:

(425" J")/(10.5" s") = 40.5" watts"

Note that 1 watt = 1 Joule per second.

Hope that helped :)