Solving 2 Rotating Discs Homework: Angular Velocities

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The discussion revolves around solving a homework problem involving two discs of different radii that come into contact and rotate with the same linear velocity. The larger disc has an initial angular velocity ω, while the smaller disc's radius is half that of the larger. The key equations used include the relationships between angular velocity, radius, and moment of inertia. Participants explore the conservation of angular momentum and the forces exerted between the discs, ultimately arriving at equations for the angular velocities of both discs. The final answers suggest that the angular velocities are dependent on the ratio of their radii, confirming the solution's validity.
  • #31
person123 said:
Alright. I finally think I have the answer... They both follow the format of ##IΔω=F_{f}rt## . I divided one by the other, leaving me with:

##\frac {r_{2}^4(ω_{2}-ω_{1})} {r_{1}^4ω_{1}}=-\frac {r_{2}} {r_{1}}##

. When simplifying and substituting the values for r1 and r2, it gave me:

##ω_{2}=\frac {ωr_{2}^2} {r_{1}^2+r_{2}^2}##
##ω_{1}=\frac {r_{2}^3ω} {r_{1}^3+r_{1}r_{2}^2}##
I arrived at the same answer, which I posted on his YouTube video, this morning. As of 3:30 PM central time today, he has not released it to the public view. So I'm going to assume it is probably correct.
 
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  • #32
scottdave said:
I arrived at the same answer, which I posted on his YouTube video, this morning. As of 3:30 PM central time today, he has not released it to the public view. So I'm going to assume it is probably correct.
:smile: At last! I'm just going to wait a while to make sure I got it, and then I'll close the thread.
 
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