posted by Joseph .
A 15 ft plank of mass 50 kg is laid across two ladders. The ladders are 5 ft apart, and the plank is laid such that 5 ft of it hang off at each end. You have a mass of 90 kg.
(a) How far out past the ladder can you walk before it gets dangerous?
I tried doing
and sloved for r2= 1.56, but the computer keeps saying its wrong.