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Simple Harmonic Motion (easy question)

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

    A 0.26 kg mass attached to a spring undergoes simple harmonic motion with a period of 0.84 s. What is the force constant of the spring?

    2. Relevant equations

    T = 2*pi*SQRT(m/k)

    3. The attempt at a solution

    I know this is supposed to be an easy question, but for some reason I can't do it. Here is what I got (which is not right):

    T = 2*pi*SQRT(m/k) and to solve for "k":

    K = 2*pi*SQRT(m)[whole thing divided by .84 seconds] = 3.814 N/m

    Ok, so what am I doing wrong? Thanks!
     
  2. jcsd
  3. Aug 1, 2009 #2

    cepheid

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    Staff Emeritus
    Science Advisor
    Gold Member

    Your algebra doesn't look right. To solve for k, you want to get it by itself on one side of the equation, which involves:

    1. Getting rid of the 2pi (by dividing both sides of the equation by 2pi).
    2. Getting rid of the square root (by squaring both sides).
    3. Getting k on top (taking the reciprocal of both sides)
    4. Getting rid of the m (multiplying both sides by m)
     
  4. Aug 1, 2009 #3
    It might make it more clear if it looked like this:

    [tex]T=2\pi \sqrt{\frac{m}{k}}[/tex]

    Now solve for k.

    HINT: Squaring both sides gets rid of the square root.
     
  5. Aug 1, 2009 #4
    ok so K = (2*pi*m)/T^2

    That gives me 2.315 N/m which is also incorrect. Hmm... I don't know.
     
  6. Aug 1, 2009 #5
    You forgot to square the 2*Pi
     
  7. Aug 1, 2009 #6
    Problem solved. Thank you
     
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