Perpetual motion in action? (no, but I can't figure it out)

I’m completely stumped. My family and I rented a beach house last week as part of our vacation. On one of the shelves in the living room is one of those chrome and plastic visual pieces that they sell in places like Spencer’s in the mall. I don’t know how to include an illustration.

It consists of a black rectangular base about 6"x1". There are two, thin, clear, plastic sheets mounted vertically on the base. These are about 3" high and 8" long. The top edge is cut so that they form a shallow V. They are parallel to each other and about 1" apart. There is a separate wheel-like piece which consists of a hub with two stubs sticking either side like an axle and three spokes, each with a diamond-shaped weight at the end of it.

You set the “wheel” on top of the plastic “walls” and it rolls merrily back and forth from one end to the other, eventually (one would assume) slowing down to the point where you need to set it going again. The point of my question is: That thing has been rolling non-stop since we moved in to the house 10 days ago without anybody touching it. It never gets lower. I can tell because on the right side, it rolls all the way to the stops at the end, just like it has since day one. It doesn’t roll as high on the left side, presumably because the shelf is not level.

Perhaps the weights at the end of the “spokes” have magnets in them, or maybe the base does. But other than increasing the downforce, it shouldn’t have any effect on the speed of the object, since any pull on a weight coming down will be counteracted by the pull on the weight going up on the other side. In the end, it should all come down to the friction of the axle on the plastic “walls”. Added to this is the friction of the hub when it rubs against the “walls,” since it doesn’t roll straight in the middle, but occasionally meanders from side to side.

So what’s the explanation? Do physics go on vacation like the rest of us? Or are the jumbo-sized Florida cockroaches playing tricks on me by keeping this thing going?

Are you sure it doesn’t have some batteries in it?

That was my thought, too. There’s a power supply somewhere. Or perhaps you suffer from blackouts, and while you’re “away” somebody else is messing with the thing. :smiley:

Got an electronic camera with you? I can tell you how to set up a yahoo account, post a pic, and put a link to the pic here. Like, pics of my new place.

A perpetual motion machine would be cool on my computer desk. Then I’d have a cool place, AND be in violation of the 2nd law of thermodynamics, though no court could sentence me for it.

I’d feel kind of like an untouchable God, like I imagine Nixon must have felt, right after the '72 election.

Why not stop the wheel and place it in the center of the device? See if it starts moving from a stand still.

I have something like that in my office and it uses batteries to create a magnetic field… It will eventually start to move in a smaller and smaller arc, and the fact that it moves higher on one side than the other probably has to do with the placement of the magnets.

Take the base apart and you’ll take the mystery apart. A battery-powered fluctuating magnetic field is responsible, same as the little spinning top that seems to keep spinning on a shallow concave plastic base forever.

I used to have one. Open up the base, and you’ll find a battery, control circuit, and an electromagnet. The wheel thing does have magnets in it. Just after each magnet passes by, the electromagnet puts out a magnetic field which repels the magnet, giving it an extra kick.

And it doesn’t start moving from a stand still. As the magnet passes by the electromagnet a current is induced, which triggers the electromagnet to turn on. If the magnet is standing still, no current is induced.

I also had a top that kept spinning on a battery-powered base. That one I still can’t figure out. It’s the same principle, of course, but the control mechanism is less obvious. It just has one electromagnet inside the base.

I think it’s called a “Springer” motor. It’s a weird little motor made from two coils, a transistor, battery, and a magnet as a “rotor.” Because of inductive delay, no matter which way the magnet approaches the coil, it will be propelled.

These things will run for at least a couple of weeks on a 9V alkaline battery.

There’s an even weirder version: a small plastic spinning top and a black base which looks like a hockey puck. Once started, the little top will keep spinning.