Force Elevator Problem!

  1. 1. The problem statement, all variables and given/known data
    Your mass is 65 kg. You stand on a bathroom scale in an elevator on Earth.

    (a) What force would the scale exert when the elevator moves up at a constant speed?

    (b) What force would the scale exert when it slows at 2.1 m/s2 while moving upward?

    (c) What force would the scale exert when it speeds up at 2.1 m/s2 wile moving downward?

    (d) What force would the scale exert when it moves downward at a constant speed?

    (e) What force would the scale exert when it slows to a stop at a constant magnitude of acceleration?

    2. Relevant equations
    f=ma
    fg=mg
    fnet=mAnet
    Ff=μῦFn


    3. The attempt at a solution
    I honestly have no idea what to do with all these Y forces going everywhere..Can someone walk me through the process of solving this problem?

    THANK YOU IN ADVANCE FOR ANY HELP!!
     
  2. jcsd
  3. PhanthomJay

    PhanthomJay 6,186
    Science Advisor
    Homework Helper
    Gold Member

    Draw free body diagrams. There are 2 forces acting on the person, the person's weight, acting down, and the normal (scale) force acting up. Use Newton's laws F_net = ma when accelerating. At constant speeed or at rest, F_net =0 (no acceleration, per newton 1). Please show an attempt .
     
  4. I found (a), (c), and (d), but I can't find (b). Here is my attempt at solving it:

    mAnet = -Fn + Fg
    mAnet - Fg = -Fn
    65(-2.1) - 65(9.81) = -Fn
    774.15 = Fn

    Help?
     
  5. I also don't understand how to find (e)..
     
  6. Okay after working on this, I've solved it. Thanks anyways!
     
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