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Elevator Forces

  1. Sep 29, 2006 #1
    Intro: A physics student of a mass 59.3kg is standing on a scale in an elecator. The scale shows the magnitude of the upward normal force (in Newtons) on the student, this value is called the apparent weight. What is the reading on the scale when the elevator:

    Questions

    a) has a constant velocity of 3.56 m/s [up] ?
    b) has a constant acceleration of 3.56 m/s squared [down] ?
    c) has a constant acceleration of 3.56 m/s squared [up] ?
    d) is undergoing freefall?

    Answer using simple Force equations, such as:
    Fnet = ma = Fg + Fn + Fapp

    a = Fnet
    m

    and other easy (grade 12) type equations. Thanks
     
  2. jcsd
  3. Sep 29, 2006 #2

    berkeman

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    Staff: Mentor

    You need to show some work on your own before we can help you. What are your answers to a-d so far?
     
  4. Sep 29, 2006 #3
    im not sure if im over thinking this or not, but i tried to think simple and i came up with......
    a) 59.3kg
    b)42.6kg
    c)76.0kg
    d)0kg
     
  5. Sep 29, 2006 #4

    berkeman

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    Staff: Mentor

    You're on the right track, but remember that weight is the force F produced on a mass m by the acceleration of gravity g. What is the equation relating force, mass and acceleration?
     
  6. Sep 29, 2006 #5
    Fnet = ma ?
     
  7. Sep 29, 2006 #6
    so would b) = 37.8 kg ?
     
  8. Sep 29, 2006 #7
    and a) = 80.8 kg ?
     
  9. Sep 29, 2006 #8
    sorry not a)...i mean c)
     
  10. Sep 29, 2006 #9

    berkeman

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    Staff: Mentor

    No. Weight has units of newtons (N), and mass has units of kg. Let's take the stationary example:

    [tex]F = mg = 59.3 kg * 9.8 \frac{m}{s^2} = ? N [/tex]
     
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