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Question about springs in series

  1. Jan 19, 2013 #1
    Please help with this question, and if possible, please explain why.

    If one spring is compressed 5 inches by a 10 pound weight. How much is two identical springs in series compressed by the same weight (total compressed distance)?
  2. jcsd
  3. Jan 19, 2013 #2
    I'll try to ask you questions to lead you to the correct answer.

    First, the way I understand the problem you have 4 objects, the weight, top spring, bottom spring, ground. Assuming that nothing is accelerating, what forces act on each object?
  4. Jan 20, 2013 #3
    The force of the weight.

    And am I correct to understand that this force acts equally on each spring?
    Which would mean that both springs (in series) are compressed the same distance as the individual spring is. Which in return would mean that the springs in series would be compressed a total distance of 10 inches(twice as much as the single spring).

    Is this correct?
  5. Jan 20, 2013 #4
    If one spring with a certain compression C exerts force F, then what force would be produced by two springs, each with compression C?
  6. Jan 20, 2013 #5


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    Homework Helper

    It is basically correct.

    The weight acts on the top spring. In equilibrium, there is no acceleration, so that force is balanced by the force of the top spring on the weight.For that, the spring has to be shortened by ΔL=F/k. (F is the external force, the weight of the object)

    The tension is the same in the whole spring, so the top spring acts with force F at the top of the bottom spring. The bottom spring balances that force in equilibrium, so it exerts F force on the top spring. For that it has to be shortened by ΔL=F/k.


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  7. Jan 20, 2013 #6
    Thank you for your answer and explanation, much appreciated!
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