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Elevator with constant acceleration

  1. Aug 23, 2012 #1
    1. The problem statement, all variables and given/known data
    The Stratosphere Tower in Las Vegas is 1137 ft high. It takes 1 min, 20 s to ascend from the ground floor to the top of the tower using the high-speed elevator. The elevator starts and ends at rest. Assume that it maintains a constant upward acceleration until it reaches its maximum speed, and then maintains a constant acceleration of equal magnitude until it comes to a stop. Find the magnitude of the acceleration of the elevator.

    The trip consists of two constant-acceleration segments, each of which has the same duration. You know the total displacement of the elevator.


    2. Relevant equations
    h = v0t + 0.5at2


    3. The attempt at a solution
    The last sentence makes me think the elevator accelerates to a certain speed, which it reaches half way up, and then decelerates with the same magnitude, stopping at the top.
    This would mean
    h = 568.5 = 0 +0.5(a)(402
    a = 0.71ft/sec

    I can't think of another way to solve this, but that isn't the correct answer.
     
  2. jcsd
  3. Aug 23, 2012 #2

    SammyS

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    For one thing, you units of acceleration are incorrect.
     
  4. Aug 23, 2012 #3
    ft/sec^2....I forgot to type the 2
     
  5. Aug 23, 2012 #4

    PhanthomJay

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    it could be a significant figure thing....a = 0.7 ft/sec^2...or perhaps a 'book' error
     
  6. Aug 24, 2012 #5
    Ok good, so you agree that I'm reading the problem correctly?
     
  7. Aug 24, 2012 #6

    PhanthomJay

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    yes.
     
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