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Question
From the diagram given below. answer the question that follows:
- What kind of pulleys are A and B?
- State the purpose of pulley B.
- What effort has to be applied at C just raise the load L = 20 kgf?
(Neglect the weight of pulley A and friction)
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Solution
1) Pulley A is a movable pulley, as it moves upward along with the load. Pulley B is a fixed pulley, as its axle is attached to the support.
2) The purpose of pulley B is to change the direction of the effort, allowing the effort to be applied conveniently downwards at point C.
3) The load is supported by two segments of the string, each exerting tension T:
L = 2T
20 = 2 T
T = 10 kgf
Since:
E = T
E = 10 kgf
Therefore, an effort of 10 kgf downward at C is required to just raise the load.
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