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Homework Help: Bucket and crank

  1. Sep 30, 2006 #1
    I have a problem of two parts which I don't know what formulas to use. I would be greatful if someone could help me with it:

    A bucket with the mass M is hanging in a cord with the length of L which in turn goes over a pulley with a diameter of D. The pulley has a crank with the length x. The force which is used at the end of the crank is F. How long must x be to make it possible to pull the bucket all the way up, L, in T seconds?

    / / Fp \ F
    II 0= I========
    I \___/
    I D
    L I
    I M I

    The second part of the problem is to identify the maximum and minimum force (Fp-max & Fp-min) on the stand (that is the axle in the middle of the pulley).

    L,M,D,F,T are known and Fp-max and Fp-min are unknown.

    What formulas should be used to solve this problem?

  2. jcsd
  3. Sep 30, 2006 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The moment applied to the pulley, which is equal to the force F applied to the crank arm of length 'x', must equal the moment applied by the mass M at diameter, D.

    The force applied by the mass M is the sum of its weight and force developed by the acceleration.

    One must determine that acceleration in terms of distance, L, and during of acceleration, T.

  4. Oct 1, 2006 #3
    thanks a lot of help
  5. Oct 1, 2006 #4
    the second question is easy when you know the first.
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