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Homework Help: The Blasted Elevator Questions; General Physics- Please help!

  1. Sep 30, 2006 #1
    hey everyone,
    sheesh, our professor has us do our homework online, and I SWEAR my answer is right, but apparently it isnt. Here is the question:

    You leave the doctors office after your annual checkup and recall that you weighed 684N. You then step onto an elevator with a scale. Find the magnitude of the elevator's acceleration if the scale reads 724N.

    How do i solve this problem?
    Thanks.
     
  2. jcsd
  3. Sep 30, 2006 #2
    Essentially, what I did was divide her weight in the drs office by 9.8, then I entered that mass into newtons 2nd law equation. I divided 724 by mass--- Doesn't that give me the acceleration?
     
  4. Sep 30, 2006 #3
    You're supposed to show your work when asking questions. We're not doing your hw for you.

    However, find the mass, m = 684/9.81 = 69.7 kg. Find the difference between your weight at rest and your weight on the accelerating elevator. 724-684 = 40 N. Now, find the acceleration. a = 40/69.7 = 0.574 m/s^2.
     
    Last edited: Sep 30, 2006
  5. Sep 30, 2006 #4
    The net force is not 724N. 724N is the sum of the normal force exerted by the elevator and your weight.
     
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