1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: 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


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