How To Find Initial Angular Velocity

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Homework Help Overview

The problem involves determining the initial angular velocity of a pendulum described by the angle function θ(t)=(0.270rad)cos(4.00t+1.00π). The context is centered around angular motion and the behavior of pendulums.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the applicability of the formula ω=2πf, with one noting that it is not suitable for the variable angular velocity of a pendulum. Questions arise about the initial conditions of the pendulum's motion and how to determine the initial angular velocity from the given angle function.

Discussion Status

Some participants have provided insights regarding the initial conditions of the pendulum, suggesting that at time t=0, the pendulum is at its highest point, leading to a zero angular velocity. There is an exploration of the reasoning behind this conclusion, but no consensus has been reached on the overall approach to the problem.

Contextual Notes

Participants are navigating the distinction between uniform circular motion and the variable motion of a pendulum, which may influence their understanding of angular velocity in this context.

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Homework Statement


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.

Homework Equations



ω=2πf

The Attempt at a Solution


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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.
 
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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.
 
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?
 
Essentially yes. Cos attains its maximum absolute value at integer multiples of pi.
 
Makes sense, thank you!
 

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