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November 21, 2014

Homework Help: physics

Posted by anonymous on Wednesday, January 17, 2007 at 6:33pm.

1. The efficiency of a squeaky pulley system is 73 percent. The pulleys are used to raise a mass to a certain height. What force is exerted on the machine if a rope is pulled 18.0 m in order to raise a 58 kg mass a height of 3.0 m?

Answer: 13.24 N?

A person lifts a 950 N box by pushing it up an incline. If the person exerts a force of 350 N along the incline, what is the mechanical advantage of the incline?

Answer: 2.71?



1. There is an ideal mechanical advantage of 18/3 = 6 in this case. The ideal force required to balance the Mg = 58*9.8 = 568.4 N weight would be 568.4/6 = 94.7 N. Because of the 73% efficiency, the actual force required is 1/0.73 = 1.37 times higher, or 129.7 N

2. 2.71 is correct

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