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Thanks!

- Thread starter MatthewPutnam
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Thanks!

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I know that moment of inertia is the integral of r^2 * dm, and I can do everything except that for r^2, I need the distance from any point (x,y,z) to the line through (0,0,0) and (1,1,1). This part has everyone here stumped!

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Tide

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Do you think the shape of the object makes any difference? :)

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I would have thought that you would need to know mass distribution of the object. Isn't that the only way you can determine the location of the centre of mass and then from that you find the distance from the axis through the centre of mass to the actual axis of rotation.

- #6

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Any physics class I took would ask for the moment

If the object has no bound, what are going to integrate from? 0 -> oo?

Anyway, this will answer your main question

The distance between a point and a line is:

d: (

where

x: the cross product.

Another way to look at it is that the distance from (x,y,z) to the line would be the the magnitude of the line to (x,y,z) times the sine of the angle inbetween: |

and using the cross product identity you get the right answer.

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