Unequal Masses on a Pivot Rod: What Does it Mean?

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Discussion Overview

The discussion revolves around a homework question involving a pivot rod with unequal masses. Participants explore the implications of treating the masses as point particles and the relevance of rotational inertia in this context.

Discussion Character

  • Homework-related
  • Conceptual clarification

Main Points Raised

  • One participant questions the meaning of treating the spheres as point particles, noting the apparent contradiction of having unequal masses while considering them negligible.
  • Another participant clarifies that treating the spheres as point particles allows for ignoring their sizes, but not their masses, and states that they have no rotational inertia about their center of mass.
  • A later reply indicates that the participant resolved their confusion by using the provided information, assuming the program correctly identified the lighter and heavier masses.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of the unequal masses and their treatment as point particles, but there is a shared understanding of the approach to the homework problem.

Contextual Notes

Some assumptions about the definitions of point particles and rotational inertia remain unresolved, particularly in relation to the unequal masses.

PSEYE
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I have a homework question that is referring to a pivot rod with unequal masses.


The spheres are small enough that they can be considered point particles.

what exactly does this mean?

I know how to solve the equation, but I'm assuming I can't use the I=2/5mr^2 to solve it.
If the masses are negligable, why are they unequal to begin with? LOL
 
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It means that you can ignore the sizes of the spheres, not their masses. (They have no rotational inertia about their center of mass.)
 
nvm, I just used what they were asking me to use, I just assumed the program knew that m_1 was lighter than m_2 and I was assuming correctly.
 
Thanks Doc Al!
 

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