Your 85-kg friend (modeled in the picture as a box) is a window-washer and leans a ladder against a large frictionless window. The bottom of the ladder is on rough cement. The ladder is 12.0 m long and is heavier at the bottom; its center of mass is 4.0 m from the lower end, and it is 45 kg. It makes an angle of 60.0 degrees relative to the floor. Your friend is 9.0 m from the bottom of the ladder.
a) What is the force from the wall on the ladder?
b) What is the normal force from the floor on the ladder?
c) What is the friction force from the floor on the ladder?
d) What is the minimum coefficient of static friction between the ladder and the floor if the ladder is not to slide out from under your friend?