Dynamics Conservation of linear and angular momentum

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Discussion Overview

The discussion revolves around the conservation of linear and angular momentum in dynamics, specifically addressing the application of these concepts in collision scenarios. Participants explore the relationships between different moments of inertia and angular velocities in the context of rotational energy and momentum equations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about why the term mvg(r) appears only on one side of the equation, contrasting it with previous experiences where it appeared on both sides.
  • Another participant suggests that it is possible to use mvGr + IGω on the right-hand side, but argues that using IAω is simpler.
  • A participant questions the meaning of r in the equation mvr + Igw = Iaw, seeking clarification on its representation as the distance from the mass center to the point of rotation.
  • One participant indicates they have resolved their confusion, implying a personal understanding has been reached.

Areas of Agreement / Disagreement

Participants express differing views on the application of terms in the equations and the interpretation of angular momentum concepts. The discussion remains unresolved regarding the specific roles of different moments of inertia and their relevance to the equations presented.

Contextual Notes

There are limitations in the clarity of definitions and assumptions regarding the points of rotation and the application of angular momentum equations, which may affect the understanding of the participants.

Dublin
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Attached file shows where my problem occurs. I understand how to get the angular momentum just before the collision. But what confuses me is is within the square. Why mvg(r) is only on the left hand side when I've had similar equations with it on both sides. Why is Ig used and why isn't Ib used for rotational energy since isn't the ω that's used is about Ib.
 

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Hi Dublin! :smile:
Dublin said:
Why mvg(r) is only on the left hand side when I've had similar equations with it on both sides. Why is Ig used …

You could use mvGr + IGωon the RHS also …

but it's much simpler to use IAω ! :wink:
… and why isn't Ib used for rotational energy since isn't the ω that's used is about Ib.

erm … no, ω is the same about any point :smile:
 
so why does mvr + Igw= Iaw? what is r suppose to represent? i thought it was just the distance of the mass center to the point of which the moment is being rotated about in this case Ia
 
Last edited:
i think i figured it out thanks
 

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