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What is considered a small velocity?

  1. Oct 7, 2012 #1
    1. The problem statement, all variables and given/known data

    An elevator is being pulled upwards with an small inital velocity. The elevator cable has a constant tension. After 250 seconds it stops with a gravitational energy of 2400J. Assume the acceleration due to gravity is 10. What is the mass of the elevator?

    2. Relevant equations

    PE=mgh

    3. The attempt at a solution

    Assume what v is then see how high it is then plug in to find m.
    -------------------------------------------------------------------------------------

    Anyway, when a problem says that something is traveling at a small velocity, but does not state what velocity to use, what should we take it as.

    This is actually what I don't like about physics. In math if I am given an integral to solve I don't assume anything, I just do it.

    I remember in thermodynamics, there was this one problem about a turbine and I tried very very hard to solve it without looking at the solutions manual. Then finally I gave up and looked at the manual and guess what. There was like 3 different assumptions you had to make an order to solve it. Thanks a lot physics.
     
  2. jcsd
  3. Oct 7, 2012 #2
    Maybe try looking up the average speed of an elevator and take half of that ... or just go with .01 m/s.
     
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