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Homework Help: Work done on a spring

  1. Mar 18, 2009 #1
    1. The problem statement, all variables and given/known data

    The amount of WORK to stretch a spring 4 feet beyond its natural length of 2 feet is 10 ft-lbs. Find the work required to stretch the spring from 4 feet to 7 feet.

    2. Relevant equations


    3. The attempt at a solution



    W=8.4 ft*lb
    Last edited: Mar 18, 2009
  2. jcsd
  3. Mar 18, 2009 #2


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    hi blessedcurse

    this would probably go better in the physics forum...

    But what is the force and energy stored in the spring at its natural length of 2ft?
    F = kx applies when x is defined as the distance form equilibrium position...
  4. Mar 18, 2009 #3
    When the spring is at it's natural position of 2 feet, x=0, so F is 0 and W is 0...

    Is that what you're asking?
  5. Mar 18, 2009 #4


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    easier to update in new posts so i can keep track of what happens...

    but yep - that looks better, first part is correct

    there is some ambiguity in the 2nd part of the question whether it means:
    ~4ft-7ft total length (2 to 5 as you have done)
    ~4ft extension from natural poistion to 7ft (would give 4 to 7)
  6. Mar 18, 2009 #5
    I fixed my previous post before you had posted, I thought.... sorry!

    I don't know... I read it as stretching it from 2 to 5 feet beyond its natural length...
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