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Homework Help: Box hanging from a rope, need to know the force.

  1. Feb 9, 2010 #1
    A 23 kg box hangs from a rope. What is the tension in the rope if the following are true?

    a)The box is at rest?
    b)The box moves up at a steady 5.0 m/s?
    c)The box has Vy = 5.0 m/s and is speeding up at 5.0 m/s^2?
    d)The box has Vy = 5.0 m/s and is slowing down at 5.0 m/s^2

    I have gotten a) = 225.4N. Because acceleration is 0. I do not know how to go about solving the other three parts though.

    I know the force of gravity is acting on the box in addition to the tension force.

    For b):
    Since velocity is constant, I would think that the forces would be in equilibrium. But apparently I am wrong. I really have no idea how to solve this.

    Any help at all would be appreciated.
  2. jcsd
  3. Feb 9, 2010 #2
    I figured it out. Now I feel stupid. Since acceleration is 0 (constant velocity), there would be no change in the force. So for b) the answer would still be 225.4N.
  4. Feb 9, 2010 #3


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    This is good, now try 'c' and 'd' using Newtons 2nd law. Welcome to PF!
  5. Feb 10, 2010 #4

    Yeah, sorry I never replied back last night. But I did get the right answers. As soon as I figured out what was going on, everything just clicked.

    What I was doing wrong for c and d was that I wasn't accounting for the the change in force. I just found the force with those particular amounts of acceleration.
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