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 8.98 m work plank which weighs 112 N and is secured with a hinge on the opposite end. Worker B will stand on the plank 4.66 m from worker A. Worker B also brings up his paint can, mc = 3.52 kg, which he places 0.370 m from where he is standing on the plank (between the two workers). Worker A unfortunately needs to supply 4.70 × 102 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

Sum the moments about the hinge:
M = 0 =470*8.98-112*8.98-B*(8.98-4.66)-3.52*9.81*(8.98-4.66+0.37)

B*4.32=4220.6-1005.76-161.95

B=706.68 N

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