Question

A uniform plank of length 6.00 m and mass 27.0 kg rests horizontally across two horizontal bars of a scaffold. The bars are 4.50 m apart, and 1.50 m of the plank hangs over one side of the scaffold. Draw a free-body diagram of the plank.

How far can a painter with a mass of 74.0 kg walk on the overhanging part of the plank before it tips?

Answer 1

Let the farthest distance of painter from center of plank be . When the painter is at this point, the plank is about to topple counter clockwise supported only by the left horizontal bar.That is but at this instant.

Net torque on the plank about the left horizontal bar is zero.

from midpoint of plank.

The painter can go a farthest distance of from mid point of plank and from Left horizontal bar.