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Thanks.Then I would like to know average speed of all particles of the sphere(relatively of me).

Quote from: simplified on 10/07/2011 14:08:20Thanks.Then I would like to know average speed of all particles of the sphere(relatively of me).Ifω = angular speed of rotationR = sphere's radiusthen, if I computed correctly the integral, it should be (3/16)πωR.

If you are stationary with respect to a uniform rotating sphere in a vacuum the average velocity of all the particles in that rotating sphere is zero because there are always as many moving away from you as there are moving towards you.

Als I think that the average speed you quote will also depend on how close you are to the sphere.

Axe of rotating sphere is motionless relatively of me.I know mass of the sphere and speed of rotating of the sphere.The density of the sphere is homogeneous.How to define impulse of the rotating sphere relatively of me?

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Quote from: Bored chemist on 12/07/2011 06:51:18...sorry, you cannot view external links. To see them, please REGISTER or LOGIN)Then it's a silly question. The rotation of the sphere makes no difference. It might as well be a stationary lump of coal.

The "impulse" of one object on another only makes sense if the objects come into physical contact but "me" and the sphere are motionless with respect to one another but the sphere is rotating so there is no effect unless thew speeds involved are relativistic and frame dragging is involved.Re the effect of distance on average velocity let us assume first that you are some distance from the sphere and it subtends an angle of a few degrees looking at the equator and through the object integrating the relative speeds of all the particles that make up the sphere many are moving at right angles and show little velocity. no consider you are much closer and the sphere subtends say 160 degrees in your field of view there are vastly more of the particle travelling significantly towards and away from you and so the total integral of speed is much greater.

What happens if the shape is irregular and the density is not uniform?