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A single fixed pulley and a movable pulley both are separately used to lift a load of 50 kgf to the same height. Compare the efforts applied in an ideal situation.

Machines

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Answer

We know that in case of a single fixed pulley, the effort applied is equal to the load.

Hence,

Ef=LE_f = L \\[0.5em]

In the case of a movable pulley the effort needed to lift a load is equal to half the load.

Em=L2Em=50kgf2Em=25kgfEm = \dfrac{L}{2} \\[0.5em] Em = \dfrac{50 kgf}{2} \\[0.5em] \Rightarrow E_m = 25kgf \\[0.5em]

Hence, the ratio of efforts applied by the respective pulley is

EfEm=21\dfrac{Ef}{Em} = \dfrac{2}{1} \\[0.5em]

Therefore, Ef : Em = 2 : 1

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