Pulley System

  • Thread starter kiwikahuna
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Homework Statement


A pulley system has an efficiency of 76.9%. The acceleration of gravity is 9.81 m/s^2. How much of the rope must be pulled in if a force of 620 N is needed to lift a 52 kg desk 2.32 m?


Homework Equations


Force = ma
Work = force * distance

The Attempt at a Solution


Because the efficiency is 76.9%, I divided 620 N by .769 to find the amount of force that the pulley system would actually have to do. (806 N). I then found the amount of work required to lift the desk without the pulley system. 52 kg * 9.81 m/s^2 * 2.32 m = 1182.87 J
To find the distance the rope has to be pulled in, I used the work formula.
1182.87 J = 806 N * (distance)
distance =1.47 m

Pulley problems have never been my forte and I'm not sure if my attempt at this problem was right. Any help would be much appreciated!
 

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