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Zero equilibrium 0 x a force?

  1. Aug 21, 2016 #1
    Okay - a classic trap . multiplication times zero .
    I have a 3 foot bar weighing 10 lbs . its attached along its mid point to an axle . how much torque / force - do I need along its axle ( motorized ) to get it to spin 30 rpm or 60 rpm ?

    its in equilibrium , but of course it needs FORCE to move it

    I am considering Nema class stepper motors / geared 5/1 - 16 to one or 27/1 - usually these motors go to 700- rpm ...
  2. jcsd
  3. Aug 21, 2016 #2


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    Uh ... WHAT multiplication by zero?
  4. Aug 22, 2016 #3


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    Just like F = m*a for linear motion, there is an analog for rotational motion as well. A torque will be required to accelerate the bar, but once it's moving only air drag and friction will slow it down.

    See here: https://en.wikipedia.org/wiki/Angular_acceleration
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