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?

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Answer 1 · 2017-12-08T05:47:31

$40.5 watts$ $40.5 " watts"$

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

$P = \frac{d W}{d t}$ $P = (dW)/dt$

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

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

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

$\frac{425 J}{10.5 s} = 40.5 watts$ $(425" J")/(10.5" s") = 40.5" watts"$

Note that 1 watt = 1 Joule per second.

Hope that helped :)