A young work crew is trying to quickly finish some touch-up painting to complete

Question

A young work crew is trying to quickly finish some touch-up painting to complete a job. Rather than setting up a secure work area, they decide to try a shortcut. Worker A will hold the far end of a 9.47 m work plank which weighs 112 N and is secured with a hinge on the opposite end. Worker B will stand on the plank 4.88 m from worker A. Worker B also brings up his paint can, mc = 3.56 kg, which he places 0.400 m from where he is standing on the plank (between the two workers). Worker A unfortunately needs to supply 483 N of force to hold the end of the plank. How much does worker B weigh? The acceleration due to gravity is g = 9.81 m/s2.

Explanation / Answer

torques are balanced... call the weight of worker B "W"

then

483 * 9.47 = WB *(9.47-4.88) + 3.56*9.81*(9.47+0.4-4.88 ) + 112 * 4.735

4574 = 4.59 WB + 174.268 + 530.32

WB= 843 Newtons

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