How Can Angular Momentum Be Described for a Rotating and Translating Disk?

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Homework Help Overview

The discussion revolves around the angular momentum of a disk that is both rotating and translating in the xy-plane. The original poster describes a disk with mass and radius, rotating with a specified angular velocity while translating parallel to the y-axis. The focus is on how to express the angular momentum and its components in relation to a coordinate system.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants explore how to calculate the total angular momentum by considering both the rotation about the center of mass and the translation of the disk. There are questions about the applicability of the parallel axis theorem and how to define angular momentum for the translational motion.

Discussion Status

Some participants have provided insights into the components of angular momentum and the relationship between rotation and translation. The discussion is ongoing, with various interpretations being explored regarding the definitions and calculations involved.

Contextual Notes

There is mention of specific parameters such as mass, radius, angular velocity, and translational speed, but the original poster notes uncertainty about how to apply certain principles, indicating potential gaps in information or understanding.

Zenshin
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Hello. Could anyone give me a hint in this problem? There´s a disk (mass m ad radius a) rotating with angular velocity w0 (only rotation). If this disk is translating in xy plane, parallel with the y-axis with its center aligned at x0, how ca I describe the angular momentum L (t), and it´s components, Lx Ly and Lz (with respect with the xyz coordinate system). Any ideas? (I think it´ll have variational Lx and Ly and a fixed Lz)

Thanks in advance.
 
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I assume you are given the translational speed?

In any case, the total angular momentum is the sum of:
(1) angular momentum of the disk due to its rotation about the center of mass
(2) angular momentum of the disk due to the translation of its center of mass (consider the mass concentrated at the center of mass)​
 
Oh yes, I forgot, the translation velocity is also given (v). But, since the disc translates in a linear way (it only rotates about itself), how can I define a angular momentum of it's translation? I think the parallel axis theorem (Steiner) doesn't apply here.

Thanks
 
The angular momentum (with respect to the origin) of a moving particle is defined as [itex]\vec{L} = \vec{r}\times\vec{p}[/itex], where [itex]\vec{p}[/itex] is the linear momentum and [itex]\vec{r}[/itex] is the position vector.
 

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