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Velocity of an Elevator

  1. Sep 17, 2012 #1
    1. The problem statement, all variables and given/known data

    In the sketch at right, the winch W draws the cable at a constant rate of 2 m/s.
    Calculate the velocity of the counterweight C relative to the elevator E.

    2. Relevant equations

    (Sa-Sc)+(Sb-Sc)+Sb=I2

    3. The attempt at a solution

    I must be using the wrong equation because I am getting really strange answers.
     

    Attached Files:

  2. jcsd
  3. Sep 17, 2012 #2

    NascentOxygen

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    Staff: Mentor

    Perhaps, perhaps not, we're unable to say either way since you haven't included your working for us to see what equation/s you are using.

    Q: How fast is the elevator rising?
     
  4. Sep 19, 2012 #3
    I used 4Vw +Vc = 0. Which means the elevator would rise at 8m/s but that can't be right.
     
  5. Sep 19, 2012 #4

    CWatters

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    Science Advisor
    Homework Helper

    Think about it in terms of the amount of rope wound in. If the winch winds in 2m the elevator goes up 1m. So the elevator moves up at half the speed of the winch eg 1m/s

    Then look at the elevator and counter weight. If the elevator were raised say 1 meter how far does the counterweight move relative to the platform? How far does it move relative to the elevator?
     
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