1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    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!

Torsional Pendulum

  1. Dec 2, 2009 #1
    1. The problem statement, all variables and given/known data

    https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2111/fall/homework/Ch-15-SHM/torsion-pendulum/4.gif [Broken]

    A uniform meter stick is hung at its center from a thin wire. It is twisted and oscillates with a period of 5 s. The meter stick is then sawed off to a length of 0.76 m, rebalanced at its center, and set into oscillation.

    With what period does it now oscillate?

    L = 1m
    L(final) = 0.76m
    T = 5s

    2. Relevant equations

    Moment of Inertia: I = (1/12)*M*L^2
    period: T = 2pi*sqrt(I/K) Where K is the torsional constant

    3. The attempt at a solution

    I first found the torsional constant:

    K = [(1/12)*M*(1^2)]/[(T/(2pi))^2] = 0.13459M

    So no I have K = 0.13459M

    T(final) = 2pi*[sqrt((1/12)*M*(0.76^2)/0.13159M)] = 3.8s

    The answer looks correct but I'm not sure, any ideas? Thanks!
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 2, 2009 #2
    instead of going for so much calculation...
    u could have done it like this....



    and u have I=(M*L^2)/12

    so jus take the ratio

    T1/T2=L1/L2 :smile:

    where T2 is the time period when the length is 0.76
    directly arrives at your answer ...
  4. Dec 2, 2009 #3
    Oh yeah it does.....cool.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Threads - Torsional Pendulum Date
Period of Vibration of Torsion Pendulum Dec 12, 2015
Torsion pendulum in Cavendish experiment Apr 18, 2015
Torsional pendulum Apr 18, 2014
Torsional Pendulum Experiment Help Jul 31, 2012
Torsion pendulum Dec 2, 2011