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Pulley Problem With Tension Direction

  1. Mar 20, 2013 #1
    In the attached picture, one sees a pulley with a mass which is holding two different weights. In chegg, the tension due to a weight is represented as a downward direction. Then, when the tension is seen in relation to the pulley, the direction switches for both weights. WHY IS THIS?!

    pulley2.jpg

    Thanks,
    Cameron
     
  2. jcsd
  3. Mar 20, 2013 #2
    What problem is it? Can you tell me what it is or what problem from chegg you are trying to understand?
     
  4. Mar 20, 2013 #3
    The two blocks in the figure are connected by a massless rope that passes over a pulley. The pulley is 12cm in diameter and has a mass of 2kg. As the pulley turns, friction at the axle exerts a torque of magnitude 0.5Nm. If the blocks are released from rest, how long does it take the 4 kg block to reach the floor?
     
  5. Mar 20, 2013 #4

    haruspex

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    It's standard action and reaction. A weight pulls down on a string with an equal and opposite force to that with which the string pulls up on the weight. Similarly between string and pulley, and between each little section of string and its neighbours.
     
  6. Mar 20, 2013 #5

    tiny-tim

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    Hi Cameron! :smile:
    Tension is a force.

    The tensions at the two ends of a rope are opposite (and equal in magnitude if the rope is massless). :wink:
     
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