Bizzare center of gravity problem.

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Discussion Overview

The discussion revolves around the concept of the center of gravity for a system of two equal masses and its relationship to the center of mass. Participants explore the definition and implications of these concepts in the context of a specific problem involving gravitational fields and distances.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the definition of the center of gravity for a system of free particles, noting a lack of reference in their materials.
  • Another participant suggests that in most contexts, the center of gravity is equivalent to the center of mass.
  • A subsequent post indicates that the problem implies a distinction, as it asks about the behavior of the center of gravity as the distance y approaches infinity and zero.
  • A participant provides a definition of the center of gravity, explaining it as the point where the entire mass could be placed to replicate the gravitational force at a specific point.
  • There is a question raised about when the center of gravity is not identical to the center of mass, with a response indicating it occurs in non-uniform gravitational fields.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the definition of the center of gravity for free particle systems, and there is no consensus on whether the center of gravity and center of mass are identical in this context. Multiple views on the topic remain present.

Contextual Notes

The discussion highlights limitations in understanding the center of gravity in relation to gravitational fields and the specific conditions under which the two concepts may differ.

quasar987
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Here's the question: "Two equal masses m are separated by a distance a. Find the center of gravity of the two masses relative to a point P on the perpendicular bisector of the line joining them a distance y from the midpoint between them."

(perpendicular bisector definition)

I never heard of a definition of a center of gravity for a system of free particles. Not in my book nor on the net. Any clue?

Thx.
 
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In most contexts, center of gravity is identical to center of mass. Is that the case here?
 
Probably not as the next question is: "Show that as y aproaches infinity, the center of gravity approaches the center of mass. What happens when y approaches 0?"

But I wouldn't know anyway because I don't know what the center of gravity is for a system of free particles.
 
center of gravity

OK... just checking.

The center of gravity of a system of particles, with respect to some point, is the location where you could put the entire mass and still get the same gravitational force at that point.

So: Find the net gravitational field at point P due to the two masses. Then find where you'd have to put the entire mass (2m) to duplicate that net gravitational field at point P. That point is the center of gravity.

(It's easy.)
 
Ok, thanks a lot for clarifying that !
 
question- when is center of gravity not identical to center of mass?
 
daveed said:
question- when is center of gravity not identical to center of mass?
In a non-uniform gravitational field.
 

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