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Homework Help: Physics 20-1: Energy

  1. Jan 8, 2009 #1
    1. The problem statement, all variables and given/known data
    This is a question from a test i had today..i wanna know if I did it right or not.

    A mass on a spring with spring constant 700 N/m is compressed 16 cm. If the maximum value of the speed is 12 m/s, what is the mass of the mass in kg?

    2. Relevant equations

    Ep = 1/2kx^2, Ek = 1/2mv^2

    3. The attempt at a solution

    so conservation of energy plays a role in this...

    Vmax = 12 m/s
    k = 700 N/m
    x = 0.16 m
    m = ?

    Ep = Ek
    1/2kx^2 = 1/2mv^2
    m = (1/2kx^2) / (1/2v^2)
    m = 0.12 kg.

    im really doubting myself right now.
  2. jcsd
  3. Jan 9, 2009 #2
    Looks ok to me, but then again it is 1:30 A.M and im borderline asleep...
  4. Jan 9, 2009 #3
    lol. well thanks i guess. but a whole bunch of other people in my class got something else. it's wierd.
  5. Jan 9, 2009 #4
    Did the problem statement tell that whether the spring was vertical or horizonal?
    if it's vertical ,the answer will be different.
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