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Homework Help: Spring oscillation

  1. Nov 17, 2014 #1
    1. The problem statement, all variables and given/known data

    A block with mass m is attached to the end of a spring with a constant spring k. It oscillates with a period of 2 seconds when pulled. When an additional 2 kg is add to the block it oscillates with a new period of 3 seconds. What is the mass of the black and the spring constant K?

    2. Relevant equations
    T = 2pi*sqrt (m+2/k) my apologies for the format. The symbols will not post for some reason.

    3. The attempt at a solution
    I attempted to use the about equation above and solve for m. Of course I ran into the problem that I do not know the spring constant k as well. I tried to find K by use the equation and solving for k by imputting the mass of the second block. However I am not confident because the period T at 3 seconds is when the masses are added together and not just for the 2 kg mass alone.

    I am fine with the algrebra if I can just start the equation. Any help would be greatly appreciated.
  2. jcsd
  3. Nov 17, 2014 #2


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    You have two values for T, so that's two equations. For two unknowns. A little algebra and both come out just fine !
  4. Nov 17, 2014 #3
    Thank you for the response. Does this mean I solve both Period equations for k first then solve for mass?
  5. Nov 17, 2014 #4
    When solving for k: k =(8pi2)/4 = 2pi2
    When solving for m: m = ((kT2)/(4pi2)) - 2
  6. Nov 17, 2014 #5
    That is not the right way to do this.

    You have
    T1 = 2pi*sqrt (m/k)
    T2= 2pi*sqrt ((m+2)/k)
    Now solve both equations for k because k is a constant and don't substitute anything in yet. Then you can set k's equal to each other and solve for m. After knowing the mass of the block you can calculate the spring constant k.
    Last edited: Nov 17, 2014
  7. Nov 17, 2014 #6
    Awesome, thank you
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