Question

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?

Answer 1

`40.5 " watts"`

Explanation:

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

`P = (dW)/dt`

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

`P = 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 :)