Question

A man is walking on a plank which is placed horizontally across two supports so that equal length projects at each end. If the plank is 5m long and has a mass of 30kg, what is the greatest distance from each end at which the support can be placed so that a man of mass 80kg can stand anywhere on the plank without it falling off the supports?

Answer 1

$$Mx=m(0.5L-x)$$

$$80x=30(0.5(5)-x)$$

$$x=0.68\ m$$