Solving 2 Rotating Discs Homework: Angular Velocities

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Homework Help Overview

The discussion revolves around a problem involving two rotating discs with different radii and angular velocities. The larger disc has an initial angular velocity and the smaller disc is in contact with it, leading to a scenario where they must rotate with the same linear velocity. Participants explore the implications of this setup in terms of angular momentum and energy conservation.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the conservation of energy and angular momentum, questioning the assumptions made about the system. Some express uncertainty about how to apply conservation laws due to the discs not being attached to the same center axle.

Discussion Status

The conversation is ongoing, with participants offering various insights and questioning each other's reasoning. There is an exploration of the relationship between mass, radius, and moment of inertia, as well as the forces exerted between the discs. Some guidance has been provided regarding the need to consider external forces and torques.

Contextual Notes

Participants note that the problem may involve complexities due to friction and the nature of the forces between the discs, which could affect the conservation principles being applied. There is also mention of external forces that may influence the system's behavior.

  • #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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