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Homework Help: Kinetic frictions, pulleys, and Newton's third law

  1. Oct 4, 2011 #1
    1. The problem statement, all variables and given/known data
    Block A and B are connected by a string passing over an essentially frictionless pulley. (Block A is on a horizontal plane, while block B is suspended in the air) When the blocks are moving block A experiences a force of kinetic friction of magnitude 5.7N. If mA= 2.7kg and mB= 3.7kg calculate the magnitude of:
    (a) The acceleration of the blocks
    (b) The tension in the string


    2. Relevant equations
    ƩFx=ma(x)
    ƩFy=ma(y)
    a(x)= ƩFx/m
    Fnet(a)= Ft=Fk
    Fnet(b)= Fg-Ft
    Ft(b)=Ft(a)



    3. The attempt at a solution
    ƩF(a)= Ft-Fk
    = Ft- 5.7N
    ƩF(b)= Fg-Ft
    = mg-Ft
    =(3.7kg)(9.8N)-Ft
    =36.26N-Ft
     
  2. jcsd
  3. Oct 5, 2011 #2
    Does the following look like I'm on the right track?
     

    Attached Files:

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