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Two different springs in parallel

  1. Feb 13, 2015 #1
    1. The problem statement, all variables and given/known data

    In a parallel spring system, the springs are positioned so that the 56N stretches each spring equally. The spring constant for the left-hand spring, kl, is 1.7Nm and the spring constant for the right-hand spring, kr, is 7.7Nm.

    2. Relevant equations
    Momentum Principle
    ks= mg/s

    3. The attempt at a solution

    I'm confused with how they'll stretch the same length.. need help

    (1.7N/m)(56N)= 95.2m
    (7.7N/m)(56N)= 431.2m
    Last edited: Feb 13, 2015
  2. jcsd
  3. Feb 13, 2015 #2
    Check the units on your two equations.

    If each spring stretches x meters, what is the force for each of the springs (in terms of x)? If the sum of the two spring forces is 56 N, what is x equal to?

  4. Feb 13, 2015 #3


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    Staff: Mentor

    Is that the entirety of the problem statement or was there a specific question associated with the description? Is there any other context we need to be aware of? A diagram perhaps?
  5. Feb 13, 2015 #4
    Screen Shot 2015-02-13 at 5.57.38 PM.png
  6. Feb 13, 2015 #5


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    Staff: Mentor

    Ah. Much clearer! The two springs are constrained to stretch by the same amount, and both contribute to the total force that supports the weight. You have to figure out what amount of stretching will result in the desired total.
  7. Feb 13, 2015 #6
    Would I use s = mk/2k ? I am confused on this question because I am not sure how to find an equal stretch with a constant force between the two springs.
  8. Feb 13, 2015 #7
    Why don't you try answering the questions I posed in post #4? These will lead you directly to the answer.

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