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Spring constant question!

  1. Apr 21, 2007 #1
    1. The problem statement, all variables and given/known data

    A 1200 kg car rolling on a horizontal surface has speed v=65km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2m. what is the spring stiffness constant of the spring?

    2. Relevant equations

    K(final)+Us(final)=K(initial)+Us(initial)
    1/2mv^2 + 1/2k(delta x)^2= 1/2mv^2 + 1/2k(delta x)^2


    3. The attempt at a solution

    1/2(1200)(0) + 1/2k(2.2)^2 = 1/2(1200)(18.06) + 1/2k(0)^2
    k = 80867.00826 N/m :bugeye:

    The answer looks so big that it doesnt make sense to me. I converted the 65km/h to m/s.

    thanks,
    nicole!
     
  2. jcsd
  3. Apr 21, 2007 #2

    hage567

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    Homework Helper

    Well I didn't check it yet, but think of how much energy a car moving at 65 km/h has! 2.2 meters is quite a small distance for a car to come to a stop!

    EDIT: Answer looks OK to me.
     
    Last edited: Apr 21, 2007
  4. Apr 21, 2007 #3
    must be correct
    btw...its 18.06^2
    i think u hav used it in calculations but missed it here
     
  5. Apr 21, 2007 #4
    yahh i missed it here. i just double-checked my answer.
     
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