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Question
If the weight of the movable pulley is W, obtain the expression for MA, VR, and efficiency.
Solution
If the weight of the movable pulley with its frame is W, in equilibrium
E = T
L + W = 2T
Or L + W = 2E
⇒ L = 2E − W
MA =`"L"/"E"=("2E"-"W")/"E"=2-"W"/"E"`
VR will remain same, h = `"MA"/"VR"`
`=(2-"W"/"E")/2=1-"W"/(2"E")`
If W << 2E, then 2E = L
Or h = `(1-"W"/"L").`
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