A Uniform Ladder 12 Meters Long Rests Against a Vertical

Short Answer

A uniform ladder 12 meters long rests against a vertical frictionless wall,as shown in the figure.The ladder weighs 400 N and makes an angle θ = 51° with the floor.A man weighing 874 N climbs slowly up the ladder.When he is 78 m from the bottom of the ladder,it just starts to slip.What is the coefficient of static friction between the floor and the ladder?