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Question
Block A of weight 100 N rests on a frictionless inclined plane of slope angle 30° (figure). A flexible cord attached to A passes over a frictonless pulley and is connected to block B of weight W. Find the weight W for which the system is in equilibrium.
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Solution
In equilibrium, the force mg sin θ acting on block A parallel to the plane should be balanced by the tension in the string, ie.,
mg sin θ = T = F [∵ T = F given] ......(i)
And for block B, w = T = F ......(ii)
Where w is the weight of block B.
From equations (i) and (ii), we get,
w = mg sin θ
= 100 × sin 30° .....[∵ mg = 100 N]
= `100 xx 1/2` N
= 50 N
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