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Homework Help: Elevator Tension With Upward Acceleration

  1. Oct 15, 2012 #1
    1. The problem statement, all variables and given/known data

    An elevator weighing 10 000N is supported by a steel cable. Determine the tension in the cable when the elevator is accelerated upward at 3.0 m/s2


    A) 7.0kN
    B) 10.0 kN
    C)11.6 kN
    D) 13.1 kN
    E) 40.0 kN

    2. Relevant equations

    F=ma W=mg (g=9.8m/s^2)

    3. The attempt at a solution
    W=mg
    10 000=m(9.8)
    m=1020
     
  2. jcsd
  3. Oct 15, 2012 #2
    The net force (i.e. the total of all the forces) is what causes acceleration in the equation F=ma. So draw a diagram and label the forces acting on it. (Gravity and Tension) so now use the F=ma equation and plug everything in and off you go.
     
  4. Oct 15, 2012 #3
    So it would be
    W=mg
    10 000=m(9.8)
    m=1020

    F=ma
    F=1020(3)
    F=3060

    3060+10 000 = F
    F= 13.1 kN?
     
  5. Oct 15, 2012 #4
    Remember that the force of gravity is opposite the force of tension. One's up and one's down.
     
  6. Oct 15, 2012 #5
    So the 3060 would be subtracted from the elevators weight because it's accelerating upwards (against gravity) making it 7000?
     
  7. Oct 15, 2012 #6
    Oh my goodness, I'm sorry, you were right in the first place, I read it wrong. Good work! Sorry to confuse.
     
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