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Relative velocity of sliders

  1. Oct 1, 2016 #1
    1. The problem statement, all variables and given/known data
    Screen Shot 2016-10-01 at 6.08.41 PM.png

    2. Relevant equations
    Va = Va/c + Vc
    Va = 0.2 + Vc
    Vb = Vd

    3. The attempt at a solution
    I began by finding the instant centre of rotations of AB and CD. Both of these form a right angle triangle and the length of A -> ICab = 200mm and C -> ICcd = 300mm
    Va/0.2 * 0.15 = Vb
    Vc/0.3 * 0.125 = Vd
    Va/0.2 * 0.15 = Vc/0.3 * 0.125
    0.75*(0.2+Vc)=0.417(Vc)
    Vc = -0.45
    Vd = -0.1875m/s = Vb

    The answer is 0.0536m/s, but I am not sure why taking the instant centre does not work. Did I mess anything up. Thanks in advance
     
  2. jcsd
  3. Oct 1, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    I believe that your problem lies at the line indicated above. It appears to me that you've taken velocity Va to be positive to the right and Vc to be positive to the left. Then your Va + Vc = 0.2 and so Va = 0.2 - Vc.
     
  4. Oct 1, 2016 #3
    Oh, thanks. I understand now
     
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