In figure, two blocks are separated by a uniform strut attached to each block with frictionless pins. Block A weighs 400 ~N , block B weighs 300 ~N , and the strut A B weigh 200 ~N . If =0.25 under B, determine the minimum coefficient of friction under A to prevent motion.

Step-by-step solution

Consider FBD of structure. Applying equilibrium equations, A v+B v=200 ~N A_ H =B_ H (ii) From FBD of block B , B_ H +F_ B 60^ -N_ B 60^ =0N_ B 60^ -B_ V -300+F_ B 60^ =0F_ B =0.25 N_ B B_ H -0.74 N_ B =0 (iii) -B_ V +0.71 N_ B =300 FBD of block A F_ A -A_ H =0N_ A -A_ V =400 _ A = _ A N_ A _ A N_ A -A_ H =0 on solving the above equation N_ A =650 ~N , F_ A =260 ~N , F_ A = _ A N_ A _ A = 260 250 =0.4