What is the constant angular acceleration of a rotating wheel?

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Homework Help Overview

The problem involves determining the constant angular acceleration of a rotating wheel given its time, number of revolutions, and final angular speed. The context is within the subject area of rotational kinematics.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to use kinematic equations for angular motion but encounters difficulties with the initial angular velocity. Some participants suggest alternative approaches to find the initial angular velocity before applying the equations.

Discussion Status

Participants are exploring different methods to address the problem, with some providing guidance on how to rearrange equations to solve for unknowns. There is an ongoing dialogue about the relationships between the variables involved.

Contextual Notes

There is a noted uncertainty regarding the initial angular velocity and how it can be determined without knowing the angular acceleration. The discussion reflects the complexity of the problem setup and the need for careful consideration of the equations used.

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A rotating wheel requires 2.93 s to complete 37.0 revolutions. Its angular speed at the end of the 2.93 s interval is 97.1 rad/s. What is the constant angular acceleration of the wheel?

I know this should be easy. I'm just missing something. I figured 37 rev = 232 rad (=theta). Then I used the kinematic
Theta(f) = Theta(i)+(omega)(i)t+(1/2)(alpha)(t^2). But somehow it isn't working out. I know the answer should be around 15 or so but I keep getting 120 rad/sec^2!
 
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You can't use your initial equation directly because you don't know the initial velocity yet. Use ωf = (ωi) + α*t; to find ωi. Then you can plug that into your other constant acceleration question to find α. If I did it correctly, the acceleration should come out closer to 10 rad/s
 
How can you use ùf = (ùi) + á*t to find ùi when you don't know what á is?

(alright well you know what those symbols should mean)
 
You solve for ωi in terms of α and plug it into the other equation. It's a system of 2 equations with 2 unknowns.
 

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