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Homework Help: Tension on a Frictionless Surface

  1. Oct 21, 2007 #1
    A massive steel cable drags a 20 kg block across a horizontal, frictionless surface. A 100 N force applied to the cable causes the block to reach a speed of 4.0 m/s in a distance of 2.0 m.

    What is the mass of the cable?

    I hate to ask you folks for a lot of help. But I have no idea of how to solve this problem, or of how to approach this problem. If anyone could I would love a little push in the right direction but I definitely am not asking for the answer.
  2. jcsd
  3. Oct 22, 2007 #2

    solve for acceleration

    draw two your force diagrams

    Last edited: Oct 22, 2007
  4. Oct 22, 2007 #3
    Well, I was thinking about it by looking at the net forces of the rope and the block separately.

    For the rope, there is a 100 N force rightward and a T force leftward. The addition of these forces equals ma.

    Looking at the block, there is a tension force rightward which should equal the rope's tension force leftward. You can find that tension because you have the mass of the block and can find its acceleration. You can probably take it from there.

    Does that make sense to you?
  5. Oct 22, 2007 #4
    I realise that the acceleration is 4.0m/s/s; however, I wonder if there are more than two forces acting on the cable. I mean, there is the F(b on c) and the F(G).
  6. Oct 22, 2007 #5
    The force of gravity does not contribute to the acceleration.
  7. Oct 22, 2007 #6
    Thank you all very much, you were all very helpful.
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