An arrangement of two pulleys, as shown in the figure, is used to lift a 47.2-kg

Question

An arrangement of two pulleys, as shown in the figure, is used to lift a 47.2-kg mass a distance of 3.10 m above the starting point. Assume the pulleys and rope are ideal and that all rope sections are essentially vertical.

(a) What is the mechanical advantage of this system? (In other words, by what factor is the force you exert to lift the weight multiplied by the pulley system?)

(b) What is the change in the potential energy of the weight when it is lifted a distance of3.10m?

(c) How much work must be done to lift the47.2-kg mass a distance of3.10m?

(d) What length of rope must be pulled by the person lifting the weight3.10m higher in the air?

Explanation / Answer

A) I would need to see the pulley arrangement to know for sure. I am assuming one pulley lifts the second pulley and load is lifted by the second pulley. IF so, the Mechanical Advantage is 2:1 You need to pull 2 meters of rope to lift the load 1 meter. (Count the vertical ropes and subtract 1) b) PE = MGH = 47.2 kg * 9.8 m/s^2 *3.1m = 1433.94 J c) Conservation of Energy requires1433.94J d) IF my #a is correct: 3.1 * 2 = 6.2 m

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