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Spring in moving elevator!

  1. Sep 26, 2011 #1
    1. The problem statement, all variables and given/known data

    Three masses m1 = 3.1 kg, m2 = 9.3 kg and m3 = 6.2 kg hang from three identical springs in a motionless elevator. the elevator is moving downward with a velocity of v = -2.3 m/s but accelerating upward with an acceleration of a = 4.8 m/s2. (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.) What is the force the bottom spring exerts on the bottom mass?

    2. Relevant equations


    3. The attempt at a solution

    Some of my confusion lies with k. Since k is a constant is it the same value as if the elevator was motionless or does k change when the elevator moves?
  2. jcsd
  3. Sep 26, 2011 #2
    The spring constant k is constant in the elastic region of the spring. Assume this for your solution.
  4. Sep 27, 2011 #3
    Still not sure how to solve this I guess
  5. Sep 27, 2011 #4
    Draw your Free-Body Diagram first.
  6. Sep 27, 2011 #5


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    How is it this possible "... a motionless elevator. the elevator is moving " ?

    Follow flyingpig's advice !!!
  7. Sep 27, 2011 #6


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    I think he means the masses are motionless wrt the lift and not bouncing around - but yes free body diagram.
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