Rotational Motion: Finding Angle of Chalk Line on Rotating Bicycle Wheel

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Homework Help Overview

The problem involves a rotating bicycle wheel with a specified angular speed and angular acceleration, seeking to determine the angle of a chalk line drawn on the wheel after a certain time interval. The subject area pertains to rotational motion and kinematics.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of rotational kinematics equations and question the correctness of the angular acceleration value. There is an attempt to clarify the calculations and explore whether adjustments to the result, such as subtracting 2π, might be necessary.

Discussion Status

The discussion is ongoing, with participants providing corrections and suggestions for re-evaluating the calculations. There is no explicit consensus on the correct approach or final answer yet.

Contextual Notes

Participants note a potential typo in the angular acceleration value and express uncertainty about the calculations leading to the angle determination. There is an implication that the original poster may be overlooking a simple mistake in their reasoning.

AJDangles
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Homework Statement


A rotating bicycle wheel has an angular speed of 2.84 rad/s at some instant of time. It is then given an angular acceleration of 1.75 rad/s2. A chalk line drawn on the wheel is horizontal at t = 0. What angle does this line make with its original direction at t = 1.77 s?

Homework Equations



The rotational kinematics equations.

The Attempt at a Solution



Using the equation:

Δθ = ωt + (1/2)(ang. accn)t2

= (2.84)(1.77) + 0.5 (1.75)(1.77)^2
= 7.77rad

I can't get it right. I have a feeling I have to use the angular acceleration to change the angular velocity, but I can't figure out how to do this. It's probably something really silly so if someone could point out what I'm doing wrong it would be much appreciated.
 
Last edited:
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Angular acceleration is 1.75, not 1.62
 
ahsanxr said:
Angular acceleration is 1.75, not 1.62

Sorry, typo. Fixed now. Answer is still wrong.
 
Anybody?
 
Maybe you should subtract 2pi from the answer?
 

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