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Homework Help: Blocks being pulled by a string

  1. Mar 23, 2005 #1
    I'm just starting to get my head around the concepts of Tension and Force but I'm stuck on this question, I was wondering if anyone could help me out?

    Q: 3 identical blocks connected by ideal strings are being pulled along a horizontal frictionless surface by a horizontal force F. The magnitude of the tension in the string between blocks B and C is T. Assume that each block has mass m.

    i> What is the magnitude of the force? (Expressed in terms of T)
    ii> What is the magnitude of the accleration of the three blocks (in terms of m and F)?

    I worked out the acceleration on block B (T/(2*m)) but don't know what to do next. I'd really appreciate any help with this.

    Attached Files:

    Last edited: Mar 23, 2005
  2. jcsd
  3. Mar 23, 2005 #2
    The acceleration is the same for the entire system. So the force must be (m1 + m2 + m3)*a

    hope that helps
  4. Mar 23, 2005 #3
    I think it does... that would make the Force 3/2*T right?
    So in terms of m and F, the acceleration would be F/3m ?
    Last edited: Mar 23, 2005
  5. Mar 23, 2005 #4
    Yes, you are right.

    [tex]F - T = m_ca[/tex],


    [tex]F = T + m_ca = T + m(\frac{T}{2m}) = \frac{3}{2}T[/tex]
  6. Mar 23, 2005 #5
    Awesome - Thanks a lot
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