November 1st, 2016, 03:53 AM  #1 
Member Joined: May 2016 From: Ireland Posts: 96 Thanks: 1  pulley system
Two particles A and B each of mass m are connected by a light inextensible string passing over a light, smooth, fixed pulley. Particle A rests on a rough plane inclined at α to the horizontal, where tan α =5/12 . Particle B hangs vertically 1 m above the ground. The coefficient of friction between A and the inclined plane is .5 The system is released from rest. (ii) How far will A travel after B strikes the ground? i know how to work out most of this question. the only thing i am confused on is what is the acceleration of mass of A when B strikes the ground. i would of said it was g/13 but it is 11g/13 . all i need to know is the acceleration of B. 
November 1st, 2016, 06:34 AM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 2,640 Thanks: 1319 
when B hits the ground, the tension force in the string becomes zero, therefore the net force on particle A is the force of kinetic friction + force component of gravity down the incline ... $ma = \mu mg\cos{\alpha}  mg\sin{\alpha}$ $a = \mu g\cos{\alpha} g\sin{\alpha}$ $a = \dfrac{1}{2}g \cdot \dfrac{12}{13}  g \cdot \dfrac{5}{13} = g\cdot \dfrac{11}{13}$ 
November 1st, 2016, 07:22 AM  #3 
Member Joined: May 2016 From: Ireland Posts: 96 Thanks: 1 
Thanks thats what I needed to know tension is zero when b hits the ground


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