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Let's say I have a spinning steel ball that I have somehow managed to be completely free in all axes of movement. If I fire a BB at it with enough force on a north-south (to the ball) angle, what will happen. Will it start to wobble by a certain amount? Will it change it's orientation and then stay there? I welcome complex answers, but please summarize them in laymen's terms as well.

When I say north-south, I'm referring to the earth so that means it would be fired along a plane of the axis of the spin at about 45 degrees (or whatever) to the axis if that makes any sense. In other words, not with or opposing the spin, just perpendicular to it at an angle.

Arlen Beiler
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    Can you be a bit more descriptive about what you mean by "north-south (to the ball) angle?" – joshphysics Feb 01 '13 at 23:16
  • "with enough force" you could completely destroy the gyroscope, along with the building it is in. So this needs some more precision as well. :D – Michael Apr 03 '13 at 02:59

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Well if we assume an ideal BB and sphere then any force on the sphere will be normal to the surface therefore the only consequence would be that the sphere would start to move away from the point of impact.

If some sort of frictional effect occurs on impact then things become more complex. I imagine that the interesting part of the question could be couched in terms of a tangential force acting momentarily on the surface of a spinning weightless sphere. However I believe under no circumstances can a sphere wobble as the mechanism for wobbling requires the moment of inertial to be different according to the orientation of the axis.

Barack Obama
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  • Why would it have to be weightless? Or are you saying this would make it more interesting? – Arlen Beiler Feb 02 '13 at 18:36
  • If it had a weight but was not supported then it would start accelerating. If it has a weight but is supported in some fashion that doesn't otherwise affect the movement then it's mostly equivalent to the weightless case. The weightlessness is really a shorthand for establishing a frame of reference to contrast the initial situation and the resulting situation after the interaction has taken place. – Barack Obama Feb 04 '13 at 00:16