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Homework Help: Minimum time for a tension

  1. Nov 13, 2006 #1
    a) What is the minimum time in which one can hoist a 1.00-kg rock height of 10.0m if the string used to pull the rock up has a breaking strength of 10.8 N? Assume the rock to be initially at rest.

    b) If the string is replaced by one that is 50% stronger, by what percentage will the minimum time for the hoist be reduced.


    i just used a= 2(x-xo)/t^2 and then i got 2(10)/t^2 = 10.8/1
    so i got 10.8=20/t^2 and so t would be root 10.8 but the answer is 4.5seconds... how?

    b) i need to get a) to solve this...
  2. jcsd
  3. Nov 13, 2006 #2
    Hint 1: Draw a free body diagram for the rock.
    Hint 2: There is some provided info in the problem you haven't used yet.
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