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aspirare21

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## Homework Statement

A girl weighing 470N hangs suspended on the end of a rope 8 meters long. What will be her gain in potential energy when a boy swings her to one side so that the rope makes an angle of 35º with the vertical? gravity= 9.7 m/sec²

I need the answer to be exactly 679.5 Joules.. My professor wants that I use an equation with Fg? (Free body diagram)? Or any solution that will leads to the exact answer..

## Homework Equations

PE=mgh

## The Attempt at a Solution

PE''=mgh mg (470N) x h (8 meters)

=3760

PE'=mgh 470 x (cos 35º) x 8

=3080

3760-3080=680