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Homework Help: Difference between applied tension and tension due to weight?

  1. Jan 5, 2006 #1
    im trying to do this AP problem that involves a block on a table attached to a string which hangs over a pulley. in Case I 50 N is applied to the string and in Case II a 5 kg block is attached. the tension in Case I is 50, but according to my packet in case II the tension in Case II is 40. why would 50 N applied directly be more tension than Fw = 5x10 = 50 N?
  2. jcsd
  3. Jan 5, 2006 #2
    btw the block on top is 10kg and there is a coefficient of friction of .2
  4. Jan 6, 2006 #3


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    Gold Member

    Because in the second case there is more mass so there's less acceleration:
    mg - Fs = (M+m)a
    50 - 20 = 15a
    a = 2
    Now looking at the 5kg weight:
    50 - T = 5a
    T = 50 - 10 = 40
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