A small box is held in place against a rough wall by someone pushing on it with a force directed upward at an angle of 260 above the horizontal.  The coefficient of static and kinetic friction between the box and the wall are 0.40 and 0.30, respectively.   The box slides down unless the applied force has a magnitude of 13 N.  What is the mass of the box?

A desperate hiker has to think fast to help his friend who has fallen below him. Quickly, he ties a rope to a rock of mass ma and makes his way over the ledge (see the figure). If the coefficient of maximum static friction between the rock and the ground is µ, and the mass of the hiker is mâ, what is the maximum mass of the friend, mc, that the rock can hold so the hikers can then make their way up over the ledge? Assume the rope is parallel to the ground and the point where the rope passes over the ledge is frictionless. mc = Ju

A flatbed truck is carrying a 30-kg crate up a sloping road at a constant speed. The coefficient of static friction between the crate and the bed is 0.60, and the coefficient of kinetic friction is 0.25. What is the maximum angle of the slope that the truck can climb if the crate is to stay in place? Answer in degrees.

A patient with a broken tibia has the lower half of his leg suspended horizontally by a cable attached to the center of his foot. The tension in the cable needs to exert a force of F, = 25 N horizontally for traction and F, = 30 N vertically upward to support the leg. Find the magnitude of the tension in the cable. Hint: Put the center of the patient's foot at the origin of the xy-plane. Pulley F₂ x F₁ (Give your answer to one decimal place. Use symbolic notation and fractions where needed.) Flension N