Weight of Block

Problem 539
The block A in Fig. P-539 supports a load W = 100 kN and is to be raised by forcing the wedge B under it. The angle of friction for all surfaces in contact is f = 15°. If the wedge had a weight of 40 kN, what value of P would be required (a) to start the wedge under the block and (b) to pull the wedge out from under the block?
 

Problem 536
in Fig. P-536, determine the minimum weight of block B that will keep it at rest while a force P starts blocks A up the incline surface of B. The weight of A is 100 lb and the angle of friction for all surfaces in contact is 15°.
 

Problem 521
In Fig. P-519, if μ = 0.30 under both blocks and A weighs 400 lb, find the maximum weight of B that can be started up the incline by applying to A a rightward force P of 500 lb.
 

Problem 519
In Fig. P-519, two blocks are connected by a solid strut attached to each block with frictionless pins. If the coefficient of friction under each block is 0.25 and B weighs 2700 N, find the minimum weight of A to prevent motion.
 

Problem 510
What weight W is necessary to start the system of blocks shown in Fig. P-510 moving to the right? The coefficient of friction is 0.10 and the pulleys are assumed to be frictionless.