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?

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Answer 1 · 2016-04-18T14:46:34

$683.79 J$ $683.79 J$

Be careful with that bag !!

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

Hence the work done is:

$(21 \times 9.8 + 91.5) N \times 2.3 m = 683.79 J$ $(21xx9.8+91.5)Nxx2.3m = 683.79 J$