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Homework Help: Pendulum problem

  1. Apr 2, 2010 #1
    1. The problem statement, all variables and given/known data
    This is not any school or any homework problem, It's just a problem I read in a book. And I dont know anything about it. So I would just like anyone to give me a brief guideline to solve this sum and please help me. (PS: dont tell me the answer, I wanna try it on my own. Though I do need a lot of guidelines.....)

    I'm a real amateur, so you guys might find this sum easy, but i don't get it.
    here it is:
    A simple pendulum of length 40cm oscillates with an angular amplitude of 0.04 rad. Find the time period.

    2. Relevant equations
    [tex]T = 2 \pi \sqrt {L/g}[/tex]
    (that's all I know.... I dont know about rad)

    3. The attempt at a solution
    Well I did think about it and came to a conclusion that since the time period doesnt depend on the amplitude of the pendulum well the time period will be:
    [tex]T = 2 \pi \sqrt {L/g}[/tex]
    [tex]T = 2 * 3.14 \sqrt {0.4m/9.8}[/tex]
    [tex]therefore T = approx. 1.26s[/tex]

    Though I dunno what the answer is...
  2. jcsd
  3. Apr 2, 2010 #2
    The equation for the period of a simple pendulum is correct. However, it assumes that the amplitude of the pendulum's swing is not too great. It it gets too large, the motion is no longer simple harmonic. Most school books will allow an angle up to about 10 degrees as "small". The conversion of an angle in radians to degrees is given by 360 degrees is equivalent to 2 pi radians.
  4. Apr 2, 2010 #3
    Got it
    when i converted the 0.04 rad into degree then I got it to be approx 2.29 degrees and since it is under 10 degrees as suggested by you my answer most probably is right and the motion is SHM.
    Is it right????(I expect a yes though I will even accept a no too)
  5. Apr 2, 2010 #4
    The answer is correct. :)
  6. Apr 2, 2010 #5
    Thanks for the help Stonebridge!!
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