A ladder of length L and negligible weight leans against a frictionless vertical wall making an angle 0 with the horizontal. The coefficient of friction between the ladder and the floor is µs. A man of weight W climbs up the ladder. Show that the maximum distance s he can climb before the ladder slips is given by s=µ„Ltan0.

the 50 lb block rests on the rough surface for which the coefficient of kin etic friction is uk=0.2

A fence post of mass m = 8 kg supports a fence with three lengths of barbed wire. The bottom wire is a distance d = 0.35 m from the ground and each wire is a distance 0.35 m above the previous one. Each of these three wires has the tension on it. For this problem, assume that the force exerted by these wires is purely horizontal. An additional guy wire is used to keep the pole upright with a tension of Fa = 490 N. The guy wire attaches to the post at a point h = 0.86 m above the ground and makes an angle of θ = 45 with respect to the horizontal. Write an expression for the tension in any one of the three fence wires.  What is the normal force that the ground exerts upward on the post?