markosheehan
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- May 12, 2016
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- 31
A light inextensible string passes over a fixed pulley A, under a movable pulley B of mass M, and then over a second fixed pulley C. A mass m is attached to one end of the string and a mass 3m is attached to the other end. The system is released from rest.
(i) Prove that the tension t in the string is given by the equation t(1/m + 1/3m)=g (g stands for gravity)
i cant prove this even though i feel like i am doing all the the right equations. the 3 equations i get by using f=ma and looking at all the particles seperately are t-mg=ma t-3mg=3mb Mg-2t=M(a/2 + b/2) a stands for the acceleration the particle of mass m. b stands for the acceleration of the particle of mass 3m. a/2 + b/2 stands for the acceleration . when i get a and b on there own from the first 2 equations and put this in for a and b in the last equation i do not get the answer required. i can post a picture of the diagram in the question if anyone needs it. any help much appreciated
(i) Prove that the tension t in the string is given by the equation t(1/m + 1/3m)=g (g stands for gravity)
i cant prove this even though i feel like i am doing all the the right equations. the 3 equations i get by using f=ma and looking at all the particles seperately are t-mg=ma t-3mg=3mb Mg-2t=M(a/2 + b/2) a stands for the acceleration the particle of mass m. b stands for the acceleration of the particle of mass 3m. a/2 + b/2 stands for the acceleration . when i get a and b on there own from the first 2 equations and put this in for a and b in the last equation i do not get the answer required. i can post a picture of the diagram in the question if anyone needs it. any help much appreciated
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