A uniform 7.9-m plank weighing 130 N lies on a platform with 3.5 m jutting off the platform. How far out on the plank from the edge of the platform can a 31-N dog walk without tipping the plank?

Answer 1

7.9/2 = 3.95
so center of plank is 3.95 from outer end
which is 3.95 - 3.5 = .45 inside the edge of the platform
so for equilibrium
130 (.45) = 31 x
x = 1.89 out from edge