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Elevator Question

  1. Sep 30, 2011 #1
    1. The problem statement, all variables and given/known data
    An elevator, complete with contents, has a mass of 2000 kg. By drawing free-body diagrams and by performing the neccesary calculations, determine the value of T ( tension) when
    a) the elevator is at rest


    2. Relevant equations



    3. The attempt at a solution
    i dont get how FN and T can be on the same Y axis together? any idea?
     
  2. jcsd
  3. Sep 30, 2011 #2

    SammyS

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    What is FN ?
     
  4. Sep 30, 2011 #3
    normal force
     
  5. Sep 30, 2011 #4
    what do you think tension is?
     
  6. Sep 30, 2011 #5
    tension is the normal force?
     
  7. Sep 30, 2011 #6

    SammyS

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    What normal force?
     
  8. Sep 30, 2011 #7
    the force that balance out weight ? o,o
     
  9. Sep 30, 2011 #8
    Start by drawing the FBD. In this case, its just the y (vertical) component: m*g(weight) DOWN , tension(whats being pulled) UP. The sum of all forces(vectors so set positive and negative values for direction) equals mass*acceleration. But remember that constant velocity or at rest indicates 0 acceleration. The sum of the two forces are equal to zero. You are given the mass, and gravity(g) is 9.8m/s^2, but T is unknown. This is as much as i can do.



    EDIT: is it at rest hanging, or on the ground... if the latter then ^ is wrong
     
  10. Sep 30, 2011 #9
    Tension is related to normal force, but it has everything to do with a force in an object such as a rope or something springy at the molecular level. It's the force that keeps the object that it holds from accelerating a bit like normal force. I believe that the normal force keeps gravity from accelerating an object during contact of earth, because of inertia (resistance to gravity). So, how do you think you can turn these words into solving this problem?
     
  11. Sep 30, 2011 #10
    "It's the force that keeps the object that it holds from accelerating a bit like normal force"

    I'm not sure if my words were exactly correct here, because I think I have done a few problems where an acceleration still existed o_O? but I hope you get the point.
     
  12. Sep 30, 2011 #11
    that quote applies to this prblem though!
     
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