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Question
Draw the diagram of a single movable pulley and obtain its mechanical advantage, velocity ratio, and efficiency.
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Solution
Since it is inconvenient to apply the effort in an upward direction, a single fixed pulley is used to change the direction of effort.
In equilibrium, L = T + T = 2T
E = T
Mechanical advantage =`"Load(L)"/"Effort(E)"=(2"T")/"T"=2`
As the effort is pulled down through a distance dE, the two segments of the thread carrying the movable pulley and the load goes up by dE/2.
Hence, dL = dE/2
Velocity ratio (VR) = `"d"_"E"/"d"_"L"`
= `"d"_"E"/("d"_"E"/2)`
= 2.
Efficiency =`"MA"/"VR"`
= `2/2`
= 1 or 100%.
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