coefficient of friction

Problem 516
Referring to Fig. P-515 if the coefficient of friction is 0.60 and θ = 30°, what force P applied to B acting down and parallel to the incline will start motion? What is the tension in the cord attached to A?
 

Problem 515
Block A in Fig. P-515 weighs 120 lb, block B weighs 200 lb, and the cord is parallel to the incline. If the coefficient of friction for all surfaces in contact is 0.25, determine the angle θ of the incline of which motion of B impends.
 

Problem 514
The 10-kN cylinder shown in Fig. P-514 is held at rest on the 30° incline by a weight P suspended from a cord wrapped around the cylinder. If slipping impends, determine P and the coefficient of friction.
 

Problem 512
A homogeneous block of weight W rests upon the incline shown in Fig. P-512. If the coefficient of friction is 0.30, determine the greatest height h at which a force P parallel to the incline may be applied so that the block will slide up the incline without tipping over.
 

Problem 509
The blocks shown in Fig. P-509 are connected by flexible, inextensible cords passing over frictionless pulleys. At A the coefficients of friction are μ_s = 0.30 and μ_k = 0.20 while at B they are μ_s = 0.40 and μ_k = 0.30. Compute the magnitude and direction of the friction force acting on each block.
 

Problem 508
The 200-lb block shown in Fig. P-508 has impending motion up the plane caused by the horizontal force of 400 lb. Determine the coefficient of static friction between the contact surfaces.
 

Problem 506
A 400 lb block is resting on a rough horizontal surface for which the coefficient of friction is 0.40. Determine the force P required to cause motion to impend if applied to the block (a) horizontally or (b) downward at 30° with the horizontal. (c) What minimum force is required to start motion?
 

Friction is the contact resistance exerted by one body when the second body moves or tends to move past the first body. Friction is a retarding force that always acts opposite to the motion or to the tendency to move.