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Finding Acceleration of Two blocks connected by a string.

  1. Apr 27, 2013 #1
    1. Two blocks made of different materials connected together by a thin cord, slide down a plane ramp inclined at an angle θ to the horizontal. The masses of the blocks are mA and mB and the coefficients of friction are μA and μB.

    GIANCOLI.ch05.p021.jpg
    PART A
    If μA < μB, determine a formula for the acceleration of block A in terms of mA, mB, and θ.
    PART B
    If μA > μB, determine a formula for the acceleration of block A in terms of mA, mB, and θ.


    3. I got Part A right, of which aA, 1= (mAgsinθ+mBgsinθ-AmAgcosθ-μBgcosθ)/(mA+mB)

    For Part B, I attempted it to solve it, and got the same answer as I did in Part A, yet MasteringPhysics says this is incorrect. Am I doing anything wrong? "The correct answer does not depend on the variables: mA, mB, or μB. "

    Thanks for the help in advance.

     
  2. jcsd
  3. Apr 27, 2013 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Hint: Do the blocks have the same acceleration?
     
  4. Apr 27, 2013 #3
    Oh, got it. I simply assumed that if μAB, then the blocks would end up touching each other and have the same acceleration;

    I see now that's not the case. I got aA, 2= g(sinθ- μAcosθ). Thanks for your quick response and help, Doc Al!
     
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