Find CG Point: Step-by-Step Guide

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Discussion Overview

The discussion revolves around methods for finding the center of gravity (CG) of an object, including practical techniques and theoretical considerations. Participants explore various approaches, including the use of torque and the relationship between center of mass (CM) and CG, with a focus on both general principles and specific examples.

Discussion Character

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

Main Points Raised

  • One participant suggests holding an object at its CG point to determine its location, indicating that it will not tip when balanced.
  • Another participant proposes hanging the object from a string to find the CG, emphasizing that the string should hang vertically.
  • Some participants mention the role of torque in finding the CG point, although the details are not fully elaborated.
  • A participant notes that for large objects, such as mountains, the center of mass (CM) and CG may not coincide, raising questions about the calculation methods for CG.
  • Another participant argues that CM and CG are generally the same, except in cases where tidal forces are significant.
  • One participant suggests that the procedure for finding CG is similar to that for CM, but with weight considered instead of mass, and highlights the variability of gravitational acceleration (g) based on location.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between center of mass and center of gravity, with some asserting they are the same in most cases, while others contend they differ for large objects. The discussion remains unresolved regarding the best methods for calculating CG.

Contextual Notes

Some participants mention specific conditions under which the CG and CM may differ, such as the influence of tidal forces and the dependence of gravitational acceleration on location. There is also a lack of consensus on the most effective methods for finding CG.

IPhO' 2008
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Can you tell me how to find CG. point.
thank you.
 
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Holding the object in your hand, find out where you can hold it so that it does not tip. That is the CG point.

p.s. welcome to Physics Forums :smile:
 
Someone tell me that it uses about torque to find CG. point.
 
Easiest way is to hang it loosely from a piece of string. The string is then always pointing at the CG.
I said loosely so that the string hangs perfectly vertically.
 
IPhO' 2008 said:
Someone tell me that it uses about torque to find CG. point.

It uses about torque to find CG. point.
 
IPhO' 2008, hopefully YellowTaxi's post has answered your question. If things are still not clear, you will have to provide more details. Please tell us what object you trying to find the center of gravity of, or give a specific example.
 
Something likes Mountain or a very big object. CM and CG point is not the same position .
I know how to calculate the CM point but I don't know to calculate the CG point.
 
I think CM and CG are the same point in most cases. The only exception would be for an object in a gravitational field where tidal forces are detectable.
 
IPhO' 2008 said:
Something likes Mountain or a very big object. CM and CG point is not the same position .
I know how to calculate the CM point but I don't know to calculate the CG point.
You would follow the same procedure as for CM, except that instead of mass m you would use the weight mg.

If your formula relies on mass density ρ, then replace that with ρg instead.

Note that g is a function of location, not a constant.
 

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