Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Frequency of oscillation (in Hz) question help! Thanks

  1. Jan 10, 2012 #1
    1. The problem statement, all variables and given/known data

    A 320 kg wooden raft floats on a lake in equilibrium. When a 75 kg man steps carefully onto the raft, it floats 3.5 cm deeper into the water. When he steps off, the raft oscillates for a while.

    I figured out that the force constant is 21,000 Nm - first off, is that correct?

    Now my QUESTION is, calculate the Frequency of oscillation (in Hz) after the man steps off the raft??????

    2. Relevant equations

    3. The attempt at a solution

    I came up with...

    2pi sqrt (m/k)

    2pi sqrt (320/21,000) = .776 Hrtz
  2. jcsd
  3. Jan 10, 2012 #2


    User Avatar
    Homework Helper

    I see you used the spring equation F = kx and found the k (agree with 21000).
    I have some reservations about treating this situation like a spring, but it makes considerable sense and I can't think of an alternative. Anyway, continuing with the spring model, you would use
    T = 2pi sqrt (m/k)
    to find the period and then the frequency.
  4. Jan 10, 2012 #3

    Simon Bridge

    User Avatar
    Science Advisor
    Homework Helper

    Your reasoning is more important than your results.

    Treated like a mass on a spring?
    (75x9.8)N was enough for 3.5cm extension is 21000Nm - well done.
    You plugged that into the equation for period of a mass on a spring :(

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook