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I'm new at classical mechanics but the text book says there is the torque in the spinning top which generated only by gravitation. It is hard to explain the situation, I've add the link.

http://hyperphysics.phy-astr.gsu.edu/hbase/mechanics/imgmech/toppre.gif

There is no rotation axis between $r$(length between the point and center of mass) and $F$(gravitation), and I don't clearly understand the procession of the torque.


I think the precssion of the spinning top is generated by the friction between the surface of the top(close with the point) and ground.

http://www2.picturepush.com/photo/a/13200825/640/13200825.png

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Static friction at the tip is responsible for the tip not circling as much as the free end, but ... static friction can only ever counter an otherwise unbalanced force along the surface. Where have you got that in the system? Besides, your idea doesn't explain how it works when you hang the gyroscope from a rope. –  dmckee May 31 '13 at 23:22
    
Friction is not a factor in gyroscopic precession. That is, an ideal spinning top, one that does not experience any friction, will precess exactly as theoretically described. There is an explanation of precession, illustrated with images, in an earlier question (answer by me, Cleonis, on december 26 of 2012) That earlier question was: What determines the direction of precession of a gyroscope? –  Cleonis Jun 1 '13 at 18:50

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