B Can magnets on a cylindrical object be used for projectiles?

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1. Mar 30, 2017

Alanay

What I mean is if I have 2 cylinder objects made out of a light wood for example with 6 or so magnets on either face spread evenly and another magnet behind it causing it to spin could it generate a good amount of torque to shoot a small projectile between the two cylinders. To give you a better image you may have seen people putting magnets on their fans and holding another magnet close to it causing the fan to rotate. I'm talking about something similar but with a lot more pull (10 kg and maybe more for the 2 outer magnets).

EDIT: If you still can't picture it imagine the left cylinder moving counter clockwise and the right cylinder moving clockwise so whatever is in between can be shot out.

2. Mar 30, 2017

Staff: Mentor

3. Mar 30, 2017

Alanay

Here

http://blob:http://imgur.com/ea934414-893d-47f6-ac60-46e228ed142c [Broken]

Last edited by a moderator: May 8, 2017
4. Mar 30, 2017

davenn

so you want to make a weapon ?

5. Mar 30, 2017

Staff: Mentor

It kind of looks more like a toy to me, but I'm still not getting it...

6. Mar 30, 2017

davenn

OK I will let you keep an eye on it
just going to PM you re such things

7. Mar 30, 2017

Staff: Mentor

Welcome to the PF.

LOL, show me the rail...?

Last edited by a moderator: May 8, 2017
8. Mar 31, 2017

Alanay

What do you mean? You can understand the concept from that image alone surely

9. Mar 31, 2017

Staff: Mentor

No, sorry. I'm not understanding what you are trying to do.

And please don't call me Shirley.

10. Mar 31, 2017

Alanay

Well, like I said imagine 2 cylinders on either side of a smooth path that are being rotated using magnets, left one going counter clockwise and the right clockwise. If you put a projectile the same width as path wouldn't the 2 cylinders shoot it out. I already know the answer my real question is what would the cylinders and path have to be made from and what kind of force would the magnets need or at least what kind of speed the cylinders need to be going.

11. Mar 31, 2017

Staff: Mentor

Rotated how using magnets? Some kind of motor arrangement? Where is the varying current flowing to generate the rotational forces?
No. If there are magnets on the rotating cylinders and you place a ferrous ball near them at the bottom, the ball will be attracted to the magnets and accelerate upward. But as it starts to exit the path at the top, it will be pulled back by the magnets, which will slow its velocity. You may get a net velocity out of the top, but it will be less than if you switched off the magnets as the ball reached its maximum velocity before exiting the channel...

12. Mar 31, 2017

Alanay

The projectile would not be magnetic. The magnets are simply used to make the cylinders spin.

13. Mar 31, 2017

Staff: Mentor

Oh, like a tennis ball launcher machine? Why not just use electric motors to spin the cylinders? They would be much more efficient.

https://i.ytimg.com/vi/oZjx7F1doGs/hqdefault.jpg

14. Mar 31, 2017

Alanay

15. Mar 31, 2017

CWatters

If you mean videos like this one..

..then you need to know it's fake.

16. Mar 31, 2017

Alanay

I'm not talking about that, more like this:

17. Mar 31, 2017

Alanay

I might as well post this question in this thread: Can you have the north and south pole aligned diagonally on a cube. So instead of 1 face being north and 1 south, you'd have 1 corner north and 1 south?

18. Mar 31, 2017

CWatters

That doesn't work either.

Permanent magnets alone cannot be used as a continuous power source. Read up on conservative forces https://en.wikipedia.org/wiki/Conservative_force . In short the force between two magnets is conservative. This means that if one magnet moves relative to the other, around any shape path such as a circle, and ends up back where it started, then the net work done or produced is zero. The fan in that video or your disk above returns to the starting position (or an equivalent) at least once per revolution, therefore it is not possible for it to do any work (it can't power a lightbulb).

However magnets can be used to store energy like a spring (eg Two magnets with their North poles together). In that case the system stores energy provided by something else (eg your hand) but it can't provide power continuously/indefinitely.

19. Mar 31, 2017

CWatters

PS This and other perpetual motion machines are banned topics according to forum rules so this thread is likely to be closed.

20. Mar 31, 2017

CWatters

Sure. You can make magnets virtually any shape you like.