Finding the tension in a pulley that rotates

  • #1

Homework Statement


pulley_zps70f8d0bc.png

[itex]m_2>m_1[/itex]
The pulley rotates.
Find the tensions, [itex]T_1, T_2, T_3[/itex]

Homework Equations


Newton's laws


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?
 

Answers and Replies

  • #2
74
6
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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