Hello everyone

I just wondered about this. Suppose we have a tire (or ball, or anything else to that extent) which is not leashed in whatever way: no axis through it, no rope hanging it etc etc. Then we place this tire on a conveyer belt, which can be of any characteristics (i.e, it can be slippery, rough or anything else). Then we turn the conveyer belt on.

Quick question:
Is there any such condition in which, when the conveyer belt is moving, the tire will rotate but not displace (in other word, spin on the spot) ?

Thanks in advance.

Is there any such condition in which, when the conveyer belt is moving, the tire will rotate but not displace (in other word, spin on the spot) ?

I don't think it'd be able to. The only way to make a round object rotate/spin "on the spot" of a conveyor belt would be if there was another force to hold it into place or to apply enough force to make the object constantly rotate in the opposite direction and at the same speed of the conveyor belt.

The only loophole in the "no axis or rope holding it" to make it work would be if the conveyor belt goes through an opening in a wall or something similar and then you can put the tire there so the wall holds the tire in place while the conveyor belt supplies the force to rotate the tire. If the belt goes left, the wall would have to be on the left side and if the belt goes right, the wall would have to be on the right side otherside the wall won't be able to hold the tire into place. Also if the wall opening that pushes against the tire isn't rounded, it'll grind against the tire and eventually wear it down or it may stick and cause the tire to tip over.

- N

There is one way of making this work with only a conveyor belt and a ball, which would be to have the distance between the top and bottom of the belt equal to the diameter of the ball, and place the ball in between the top and bottom. Otherwise, no.

it would be possibel to make it roll along the belt, then go back to the start.

if you stop the conveyer belt suddenly, then the ball rolls forward, then you spin the belt the other way, then repeat after the ball loses momentum

I see then. Thanks for answering ^_^

Quick question:
Is there any such condition in which, when the conveyer belt is moving, the tire will rotate but not displace (in other word, spin on the spot) ?

Yes, several.

1. the conveyor belt is running on rollers. The tyre is sitting between 2 rollers, so sits in a natural dip in the belt.

2. An air stream applies forces to the tyre during belt start up.

3. The tyre is given a single hit with a hammer during belt start up.

4. The tyre is given a single hit with a hamster during belt start up.
5. The tyre is given a single hit with a cheeseburger during belt start up.
6. The tyre is given a single hit with a doll during belt start up.
7. The tyre is given a single hit with a cannonball during belt start up.
8. The tyre is given a single hit with a miniature model hippoppotamus during belt start up.

9. The tyre was dropped on the belt with some initial linear momentum.

10. The tyre was dropped on the belt with some initial rotation.

11. The tyre was dropped on the belt with both the above.

12. The conveyor belt is not flat.

13. the tyre is filled with dry ice and is full of tiny puncture leaks. The escaping CO2 makes it hover on a CO2 cloud. Natural ambient air currents slowly set the tyre in motion.

14. ac electromagnetic equipment nearby induces eddy currents in the steel wheel the tyre is fitted to, causing rotational forces

15. An incredibly ugly person stands to one side of the tyre so it rotates to try to stay away as the belt moves.

16. Someone pees on the tyre thus imparting some momentum to it.

You couldnt think of one??


Lava

:D Dude, I'm not a good thinker.... :D