A man is standing on a plank of weight 100kgf pivoted at A and B as shown in figure. If the reaction force by pivot B is 66kgf, find the weight of the man.
A
50kgf
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B
60kgf
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C
70kgf
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D
80kgf
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Solution
The correct option is D80kgf Let the weight of the man be W kgf. Let reaction force at pivot A and B is RA and RB respectively. Since pivot A is at equilibrium, Clockwise moment = anticlockwise moment (W×2m)+(100kgf×5m)=(66kgf×10m) ⇒W=80kgf. Thus, the weight of the man is 80kgf.