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Spring constant

  1. Feb 20, 2006 #1
    A spring scale is stretched 10 cm when a force of 15 N is applied to it. How far apart should adjacent 1.0 N marks be on the scale?

    Why would 1.5 cm not be correct?

    Force= Spring Constant* Change in spring from rest
    15n=k*10 cm
  2. jcsd
  3. Feb 20, 2006 #2
    Wouldn't it be 0.66 cm? If there are 15 marks within 10 centimeters, there should be a mark every 2/3 of a centimeter. I may be reading this question wrong, though.
  4. Feb 20, 2006 #3
    For starters, watch the units! You are dividing N by cm! :grumpy: NOT a good habit to get into. The good news is, since you are using this k to calculate a distance in cm you can get away with it.

    F = kx
    15 N = k(10 cm)
    k = 15 N/10 cm = 1.5 N/cm.

    Now, set F = 1 N. (Since F is linear in x, this will be the separation between 1 N marks.)

    F = kx
    1 N = (15 N/cm)x
    x =1 N/(15 N/cm) = 0.66667 cm.

    My tip to all my students, anyways, is to ALWAYS write out your work, even if it seems easy enough to do in your head. (Perhaps especially when!)

  5. Feb 20, 2006 #4
    your right. I had everything flipped in my head
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