# A pulley system with 75% efficiency is set up to lift a 21kg bag of nails. The bag is lifted to a height of 2.3m by a person pulling on the rope with a force of 91.5N. What is the work done on the bag of nails by the pulley?

Apr 18, 2016

$683.79 J$

#### Explanation:

Be careful with that bag !!

The person applies a total of $\left(M g + 91.5 N\right)$ force. And the displacement is $2.3 m$.

Hence the work done is:

$\left(21 \times 9.8 + 91.5\right) N \times 2.3 m = 683.79 J$