# Can you balance anything?

I guess some balance points would be so small you couldn’t realistically balance a thing and then let go without adding enough force to get it out of balance, but if it was done with some kind of precise machinery, or if that force was taken into calculations, and the object was placed just slightly out of balance so as to be “pushed” right into it?
I guess air could be a problem, and it probably wouldn’t be realistic for a whole lot of objects, but let’s here some objections.

The only time I could really see a problem would be something that does have any material at the ‘balance point.’ For example, a cube with holes drilled through it on the center of each face, each edge and each corner.

Objects where the center of mass is located outside the objects itself, such as variants on the letter C could probably be made unbalanceable.

In order to “balance”, the object has to be dense enough & large enough that the prevailing wind / air currents won’t disturb it. In a quiet room, the object can be pretty small/light since the air currents are pretty minimal. Outdoors in a hurricane even a car won’t balance on four wheels; it’ll flip through the air and be knocked off its balance by the air currents. Fill the same car with cement and it’ll probably stay where it belongs.
In order to balance, an object must have a mass distribution which is stable over time. A water balloon doesn’t balance well since it keeps shape-shifting.

As noted by others above, there must be material at the point of center of mass. Beyond that, the material there must be rigid enough to support the total weight.

It must also be of such a shape & frictional coefficient that it can engage the point of your balance support. (I’m assuming we’re dealing with real world 3D objects where the experimental setup would be a vertical spike of suitable size/strength, and we’d try to set the object on the spike such that it would stay there for a reasonable time interval).
For example, imagine an object shaped like a S but lying on its side. The center of mass is on a nearly vertical edge. While you can easily find the CM, you can’t balance the object on it since the edge is nearly vertical and would slip off the point of your support.

Well, this thread proves I’m actually too stupid to be here.

When I first saw the title, the only thing I thought of was my checking account. Having now read all the posts, that’s still all that comes to mind.

I’d feel somewhat better about it if English wasn’t my native and only language. I guess the world should be happy I am not a scientist.

What do you wish to balance candidate objects on? A point? An edge? Or a tabletop?

For an interesting example of a smooth, solid object that will balance stably on a flat surface, see here, and here. Note that a super-egg won’t balance on a single point; it depends on there being a flat surface to “roll” on as it tilts.

Contrary to what Squink says (if I’m understanding him right), a concave object like a C can be made to balance on a point or an edge. In fact, convex objects cannot be made to balance, because the center of mass will always be above the fulcrum point. The system will be unstable, and any slight tilt no matter how tiny will be magnified until the object topples over.

But, you can balance a C or U shape pretty easily by orienting it like an upside-down U, and resting it on the central point on the “inside” of the surface. You can balance a hemi-spherical bowl like this as well. The object’s center of mass will be directly below the fulcrum point, and the system is then stable. (Assuming the fulcrum point doesn’t slip.) Small disturbances will make the object oscillate like a pendulum, but it will still tend to seek balance.

A cube is convex, and it’ll balance just fine on one of its faces. In fact, every object must have some orientation in which it’ll balance, else it’d be a perpetual motion machine.

But the answer to the OP is no: A well-sharpened pencil, for instance, cannot balance on its point for any significant amount of time, no matter how carefully you place it and isolate it from outside forces. If nothing else, the Heisenberg uncertainty principle makes it impossible to position it precisely enough (of course, in real experiments, there’d probably be a lot of other effects worse than the U. P., but that’s the one you can’t possibly avoid).

. . . on a flat surface, yes. But in the sentence immediately before the excerpt you quoted, I was talking about balancing concave objects on a point or edge. I meant that to be understood for the rest of the paragraph, when I was talking about convex objects. I probably should have made that clearer.

If you know of a convex solid that will balance on a point or edge, I’d be eager to hear about it.

Obviously, you can always balance something on at least one point. Just put it down somewhere and wait till it stops moving. Thats a balance point. The probably more interesting question is if you had an infinitely rigid object that could be precisely placed in a room with no air currents or chaos, is there always more than 1 balance point.

Any physical object can be static balanced at the center of gravity. There may be a few difficulties in locating it.
Dynamic balance requires the operating rpm and a means of adding or removing weight at specific points. Multi-speed rpm is an entirely different matter.

MEA CULPA! :smack:
You mean balance like standing an egg on end or a non-spinning top on its point!
General answer to this kind of balancing act is: “Not for long, if at all!”