1. Not finding help here? Sign up for a free 30min 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!

How To Find Initial Angular Velocity

  1. Jun 7, 2015 #1
    1. The problem statement, all variables and given/known data
    The angle of a pendulum is θ(t)=(0.270rad)cos(4.00t+1.00π), where t is in seconds.
    Determine the initial angular velocity.

    2. Relevant equations

    ω=2πf

    3. The attempt at a solution

    I solved for the frequency, which was 6.37E-1 Hz and subbed it into the formula above and got 4rad/s which is the same ω in the equation but it is wrong. Am I missing something because I can't figure out what is wrong with my method.
     
  2. jcsd
  3. Jun 7, 2015 #2

    andrewkirk

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The formula ω=2πf is not applicable to this case. That formula is for uniform circular motion, which has constant angular velocity, not for a pendulum, which has variable angular velocity.

    From the formula for θ you can deduce that initially (at time t=0) the pendulum is at its highest point, and hence at zero angular velocity.
     
  4. Jun 7, 2015 #3
    Ah okay, thanks!

    Did you just sub in 0 for t which gave you -0.270 at the θ to figure out that it was at its highest point?
     
  5. Jun 7, 2015 #4

    andrewkirk

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Essentially yes. Cos attains its maximum absolute value at integer multiples of pi.
     
  6. Jun 7, 2015 #5
    Makes sense, thank you!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: How To Find Initial Angular Velocity
Loading...