http://www.youtube.com/watch?v=ZqZKh0NGqco
I think this system provides a nice simple context in which to think about magnetic energy. The video could be used as an elicitation question. Where does the extra kinetic energy come from? The simplicity of this equipment naturally lends itself to student exploration of the feel and sound of the energy associated with interacting balls and magnets.
I am also intrigued by the ideas expressed in the attached comments on YouTube:
'Can you make a channel so the balls fall back down and feeds back in so that it can repeat continously? And, if so, what is keeping you from putting a little windmill contraption as the ball shoots out to convert a little bit of the linear energy into rotational energy? If you could do this, wouldn't that qualify as a 'free-energy' device, as you would harvest a bit of the energy gain?'
'I could bring back ball with no problem. But there is already one ball attracted to the magnet. So first this ball should be removed and then effect could be repeated. But it takes a lot of energy to remove the ball that was attracted in the first round.
The big question is: Is the kinetic energy of the ball that rolls away bigger than energy needed to remove the ball that was attracted to the magnet?'
'Can you make a channel so the balls fall back down and feeds back in so that it can repeat continously? And, if so, what is keeping you from putting a little windmill contraption as the ball shoots out to convert a little bit of the linear energy into rotational energy? If you could do this, wouldn't that qualify as a 'free-energy' device, as you would harvest a bit of the energy gain?'
'I could bring back ball with no problem. But there is already one ball attracted to the magnet. So first this ball should be removed and then effect could be repeated. But it takes a lot of energy to remove the ball that was attracted in the first round.
The big question is: Is the kinetic energy of the ball that rolls away bigger than energy needed to remove the ball that was attracted to the magnet?'
I find it so interesting (and not surprising) that people are so obsessed with free energy or perpetual motion machines. It does seem to me that a truly solid understanding of conservation of energy is missing from a lot of education.
ReplyDeleteSometimes it seems conservation is assumed by people and at other times it is ignored. How do we best get this concept across?