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Why mass of spring/string assumed negligible?

  1. Sep 18, 2010 #1
    In most questions I have encountered involving the calculation of tension in spring/string/rope, we are often asked to assume that the mass of the spring/string/rope to be insignificant. Why is this so? What effect does the mass of the spring/string/rope has on the tension of the spring/string/rope? I checked a few A-level books,none offered any satisfactory explanation.
     
  2. jcsd
  3. Sep 18, 2010 #2

    Doc Al

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    Staff: Mentor

    If the spring/string/rope is massless, then the tension is uniform throughout. (Otherwise, problems become too complicated.)
     
  4. Sep 18, 2010 #3
    Also, if the string had mass then it would also have an acceleration when it is connected to a system. You would then be needed to write the F=Ma equation for the string also.
     
  5. Sep 18, 2010 #4
    If you don't mind me asking, just how complicated things can be?
     
  6. Sep 18, 2010 #5
    I think you'd get a differential equation that either:

    1. is much more difficult to solve, or
    2. can only be solved numerically (in current practice, with a computer)

    With massless springs, it's just sines and cosines.
     
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