A uniform ladder with mass m2 and length L rests against a smooth wall. A do-it-yourself enthusiast of mass m1 stands on the ladder a distance d from the bottom (measured along the ladder). The ladder makes an angle ? with the ground. There is no friction between the wall and the ladder, but there is a frictional force of magnitude f between the floor and the ladder. N1 is the magnitude of the normal force exerted by the wall on the ladder, and N2 is the magnitude of the normal force exerted by the ground on the ladder. Throughout the problem, consider counterclockwise torques to be positive. Required:
What is the minimum coeffecient of static friction µmin required between the ladder and the ground so that the ladder does not slip?