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Homework Help: Force Problem all my answers don't work

  1. Nov 13, 2012 #1
    Assume you are on a planet similar to Earth
    where the acceleration of gravity is approximately 10 m/s
    and the positive directions for
    displacement, velocity, and acceleration are
    upward.
    At time t = 0 s, an elevator is at a displacement of x = 0 m with a velocity of v = 0 m/s.
    A student whose normal weight is 400 N
    stands on a scale in an elevator and records
    the scale reading as a function of time.

    0-5sec------400
    5-10sec-----700
    10-15sec----0
    15-20sec----200


    what is the velocity of the elevator at the end of 20 sec
     
    Last edited: Nov 13, 2012
  2. jcsd
  3. Nov 13, 2012 #2
    What does the scale measure?

    Maybe a hint: if the elevator and person are not moving, the force the scale applies to the person standing on it must equal what?
     
  4. Nov 14, 2012 #3
    You need to determine the acceleration of the student during each period. Then draw a acceleration vs time graph and integrate it up to 20 s.
     
  5. Nov 14, 2012 #4

    berkeman

    User Avatar

    Staff: Mentor

    Stop posting questions showing zero effort. You *must* show your attempt at a solution in your schoolwork posts. Check your PMs.
     
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