You are here:

Physics/Why won't this work?

Advertisement


Question
Hi,

This question is for my own learning and interest in all things physics.  Many of the gadgets that demonstrate the different principles fascinate me. I have though a lot about perpetual motion, and I am would really like to know why it doesn't work, particularly in a certain example described below.

Something like what I am talking about already exist (I believe  an this is similar to an induction, or magnetic motor). However I am not a scientist (more of a thinker), and I want to better understand this.

You take something like a bicycle wheel without the tire and metal part the tire rests on so what you have left is a freely turning wheel of spokes. On each spoke, you strategically place a neodymium magnet (with sufficient strength to have enough pull to the magnet on the adjacent spoke). It may be necessary to bond something to the south pole of each magnet to dampen the opposing force. Once all the spokes have magnets placed on them in a circle of positive magnetic attraction with little or no negative pull.  At this point, why wouldn't the wheel turn?  What if large, stationary magnets were placed at the strategic areas just you and distance around the wheel so that each spoke is also being pulled by the external forces as well?  No matter how configured, why would the wheel still not to spin using magnetic attraction?  It is my understanding that there is no way this could work, because every attempt at creating perpetual motion has failed.

Lastly, what would have to be different about the laws of physics in order for this TO work (obviously, this is theoretical)?  I'm not sure if I mean in changing the law of conservation of energy, because it seems that arranging magnetic to chase each other is only utilizing the natural properties already inherent to magnets. I would like to know as much as you're willing to tell me as I am fascinated by this concept. I thought of this as a child, but I never had access to (or time to pursue) education in this area. My physics classes spent most of their time making devices to keep eggs from breaking when dropped. It was ridiculous.

Thank you so much.

P.S. I am completely aware that for hundreds of years scientists have tried to create the exact thing I described, meeting only with failure, but I do not understand WHY it can not work.

Answer
Uhhhh....this idea would violate Newton's laws.  They are incomplete, when you consider relativity, but not incorrect.  Equal and opposite forces means that you get not net external force on your wheel.  Therefore, you get not spin.  There's just nothing to make it spin being applied from outside, and inside all the forces have to cancel out.

Indeed, you need external input of energy for this to work.  When one of your magnets pulls on another, that magnet pulls back with the same force.

Physics

All Answers


Answers by Expert:


Ask Experts

Volunteer


Dr. Stephen O. Nelson

Expertise

I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.

Experience

I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Education/Credentials
Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

©2016 About.com. All rights reserved.