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Homework Help: Finding the tension in a pulley that rotates

  1. Oct 14, 2013 #1
    1. The problem statement, all variables and given/known data
    pulley_zps70f8d0bc.png
    [itex]m_2>m_1[/itex]
    The pulley rotates.
    Find the tensions, [itex]T_1, T_2, T_3[/itex]

    2. Relevant equations
    Newton's laws


    3. The attempt at a solution
    I know how to solve the problem if the pulley doesn't rotate because the systems would be in equilibrium (Newton's first law) and dividing into 3 systems (one for each tension) you get [itex]T_1=m_1g[/itex], [itex]T_2=m_2g[/itex] and [itex]T_3=m_1g+m_2g[/itex].

    But I have no idea what changes when the pulley starts rotating. Can somebody give me some leads?
     
  2. jcsd
  3. Oct 14, 2013 #2
    Well if the pulley starts rotating it will do so in such a way so that m2 will start falling because it is more massive. The only difference here is that when you do Newtons Second Law on the system, there will be a net acceleration.
     
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