the center point can spin?

do you need two points to spin?

the center point can spin?

do you need two points to spin?

Spinning wheels are like other wheels. They have axles.

And the spindle also is loose on a shaft that acts as an axle.

No. If you rotate the point P around the point P by an angle [symbol]q[/symbol], you map it onto P.

What if you have a spinning top? Does the very very very very small particle at the center spin also? Or would that mean it is spinning at ALL directions at once?

Since there are no such things as infinitely small particles in normal physics, then the answer is: Yes, the small particle in the center spins as well. If the rotation is perfectly symmetrical, then the particle rotates on its own axis, like a miniture version of the top.

Or course, the top is more than likely going to have some wobble to its spinning, and that makes the motion of individual particles more eccentric.

I really don’t understand the question, though. I mean, what is the alternative? The middle particle just sitting there perfectly still? Chemical bonds with its neighbors would prevent that from being possible.

Well, electrons have spin, and they behave pretty much like point-size particles, barring all that quantum wierdness. Except, when you get down into that size range, with a spinning wheel, or an electron, you cannot ignore the quantum effects.

thanks, so it does not spin.

but in reality, any object/particle in the center of the wheel will be spinning on its axle, right?

I read the posts above to say that the center does spin (a wheel on a hub is a completely different thing.) **nth** read them to say the center does not spin. I personally think (independent of what has been said) that the center spins and that this is obvious. This just goes to show how hard it is to explain the obvious. [sup]**or the disprove the obvious**[/sup]

nth–Are you talking about the seeming paradox in which a point on the outside rim of a wheel travels at a high rate of speed, but a point closer to the center travels more slowly (and the center point travels not at all)?

If so, then the confusion is one of definition: the center point does not travel any linear/rotary distance (unlike, say, a point on the rim of a 3-foot-circumference wheel, which travels three feet every revolution), but it does spin/rotate. But you could point out that if you’re thinking about it that way, no other point on the entire wheel rotates–only the exact center. The rest travel/revolve.

huh?

okay, i am utterly confused.

back to square one, don’t you need two points to spin?

huh?

okay, i am utterly confused.

back to square one, don’t you need two points to spin?

What, you mean two reference points circling each other?

Look, if you have a wheel with a central hub/axle and a number of radiating spokes, you can determine that the hub rotates by observing the junction of the spokes to the hub. You will have two points (pick two opposite spokes) that are revolving around a central point (the hub) *to which they are fixed*–i.e., the hub is a solid, not a fluid, so if the points attached to it are moving in a circle, then you can deduce that it is rotating.

To take this to the nth degree, as it were, I suppose you could look at the atoms themselves, and see that the central atom was bonded to its neighbors, which were circling it. Of course, at that scale, everything becomes pretty absurd, and I wouldn’t place any bets that the motion of any one particular atom bears any relation to the motion of the entire wheel.

Your confusion stems from the fact that points, lines, and other mathematical constructs with no width can’t really exist in reality, so while a wheel spins about a “point”, anything at the center of the wheel actually has size, and so is either rotating around the wheel itself, or is spinning on its own axis if it’s perfectly in the center. By definition a “point” couldn’t rotate because it has no size.

nth – what is this question in relation to, anyway? Might help us resolve it more easily.

Also, this appears to be a question of semantics (akin to the old “does the moon rotate?” and “does the man go round the squirrel?” chestnuts). There are a number of potential definitions of “spin”.

Thank you! This was exactly my interpretation of the OP. A point is dimensionless, therefore it is not meaningful to talk about orientation or spin of a point. You can talk about points revolving around other points (sort of), but not a point rotating on its axis.

thank you.

i got it now.

so basically, any physical thing will be able to spin.

if it is not physical but only a point, it cannot spin.

but if you have a wheel, then you are talking about physical things, so the center will spin.

i hope i am correct?

a question posed to me with no real world application.