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2 weights hung off a wheel

  1. Apr 8, 2009 #1
    I tried a google search on the question im about to ask but i get everything except for what i want... :(

    I have 2 situations:
    i have 2 16Tonne weights connected to each other via cable, and then hung around a wheel so that the 2 weights hang side by side with no movement. If i then connect a motor which produces 40Nm of Torque to the wheel (assume no loss in any of the mechanical compartments), how fast would the weight accelerate and what top speed would they have (if thats even possible to calculate). (yes, one weight would go down and the other go up).

    Situation 2:
    similar to the one above except now the weights ARE NOT equal, one is 16T and the other 12T. What torque motor would i need to get the 16T weight moving upwards at 2m/s ?

    To be honest, i thought i could do this when i was asked to do something similar, but when i sat down to do it, i was lost. It's been a while since i have done any physics and as i said, google gave me nothing useful from what i could tell.

    Are these questions even answerable?

    Any help is greatly appreciated!
  2. jcsd
  3. Apr 9, 2009 #2
    These calcs are doable?
  4. Apr 10, 2009 #3


    Staff: Mentor

    Not without the radius of the wheel.

    torque = force * radius
    weight = mass * 9.8 m/s²

    For your second question the answer has units of power, not torque.
    power = force * velocity
  5. Apr 10, 2009 #4
    sorry yes, radius of wheel is 1m, (2m diameter).

    These both are hypothetical but potentially real questions with regards to vertical shaft mines. An elevator system if you like.

    So, in the case of
    1), 40 = F * 1 = 40N --> so it takes 40N of force to move it 1m/s ?

    as for 2), if i can get 1), 2 is not needed.
  6. Apr 15, 2009 #5
    for case 1)

    I think an acceleration of even 1m/s should be sufficient
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