Talk:Radius of gyration

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[edit] Comments from User:Tastemyhouse (21 April 2006)

The radius of gyration of an area with respect to a particular axis is the square root of the quotient of the area moment of inertia divided by the area. It is the distance at which the entire area must be assumed to be concentrated in order that the product of the area and the square of this distance will equal the moment of inertia of the actual area about the given axis.

I found this article next to useless - I have to assume that anyone who can understand this article already knows what radius of gyration means. So the article only really serves to refresh physicists, and give them a sense of verisimilitude. It would be a great improvement if someone could provide an explanation that wasn't in the physics equivalent of leagalese, and provide some meaningful examples of how this concept applies to the real world.

[edit] What is actually 'gyrating' ?

We need an explanation of the physical meaning of this! Something is presumably gyrating about something else, at a particular radius. One explanation might be as follows:

1)Take some complicated shape, where we know the mass (M) and the Moment of Inertia (I) about some axis. 
2)By definition, I = M.Rg^2.
3)Thus, Rg is the distance from the axis at which, if we put a point of mass M, we would have the same I as our original shape.

[This is similar to the way to analyse pendulums with non-point masses, i.e. as a point mass, but with a "dodgy" moment of inertia] RichardNeill 21:35, 15 July 2007 (UTC)

[edit] Chain length

This article seems to use N as the length of the chain in monomers, rather than the length of the chain in steps. Do you think this definition is common enough not to warrant a mention? Shinobu 11:14, 14 November 2007 (UTC)