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Homework Help: Simple Harmonic Motion - Two springs attached

  1. Mar 7, 2010 #1
    Yeah I got this question and I'm just wondering if I'm doing it right.

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

    A spring normally 10cm long and whose force constant is 150 n/m is connected to another spring normally 20cm long and whose force constant is 100 n/m. The combination is then pulled out so that its ends are 50cm apart.

    a) find the amount each spring is stretched.

    b) a 400g block on a frictionless surface is attached between the springs. find its period of oscillation.

    2. Relevant equations

    T = 2pi sqroot(m/k)
    F = kx

    3. The attempt at a solution

    Well I tried something no idea if it is correct..

    a) Made Xtotal = 0.2 because I subtracted the spring lengths
    X1 = F/150
    X2 = F/100
    (F/150)+(F/100) = 0.2
    F = 12
    Then I subbed F values back into the original 2 equations to get X values.

    b) For this question I assumed the combined force constant for the springs would be additive so
    k = 250 n/m
    m = 0.4 kg

    T = 2pi sqroot (m/k)
    = 2pi sqroot (0.4/250)
    = 0.25s (approx)

    Need to know if I'm doing this right or horribly wrong..

  2. jcsd
  3. Mar 8, 2010 #2


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    Homework Helper

    It is OK.

  4. Mar 8, 2010 #3
    Does that means i've done it right??
  5. Mar 8, 2010 #4


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    YES!!!! :smile:

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