Newton's cradle is a toy.
Isaac Newton did not invent it, nor did he invent the Laws of Motion. They just are. He uncovered what always, as far as we know, existed.
If you use this in class, do not show the kids the various permutations--they will find them if you let them be. Do not tell them it models the Law of Conservation of Momentum.
And if they ask for an explanation, tell them that everything moving (which is everything) has a certain amount of oomph, depending on how much stuff it has, and which direction it's moving. If they ask for more, tell them that we have just so much oomph in the world, no less, no more, and that it can be passed along between things.
If they ask why, tell them no one knows why. If you tell them otherwise, you will confuse them. Mutatio motus just is.
Just let them play, touching and seeing and hearing the world as it is.
You can play with a computerized version here, using different numbers of balls.
But why not just use the real thing?
Yes, I know Newton was reporting what others had already shown....
The cradle pictured is by Dominique Toussaint from Wikimedia.
Yes, I know Newton was reporting what others had already shown....
The cradle pictured is by Dominique Toussaint from Wikimedia.
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6 comments:
I'm really enjoying this series. I teach in a trade school, but thinking about misconceptions my students may never have confronted in their public education helps me a lot. Your approach reminded me very much of a college prof who writes a great physics blog -- I thought you might enjoy this discussion of momentum. He approaches thermodynamics in a similar way -- maybe your students would be up for discussing the similarites/differences between mechanical oomph and temperature oomph? Love your blog, thanks for the wonderful comments and photos.
I love "oomph", it's a great way of saying it.
It's really interesting to hear my junior physics majors debate what describes how much something would hurt if you got hit with it. Some chose momentum and some chose kinetic energy but it's interesting that they're still thinking hard about it after so many years of both personal experience and physics instruction.
Dear shiftingphases and Andy,
One of the joys of throwing words "out there" is finding other blogs that spread joy.
I've added both of you to my blog list--not because i want others to read them (though I think they're both well worth reading) but so I can find them (and enjoy them).
I am enjoying this series (even on my supposed PLN Sabbatical). However, I am wondering when you will add electron microscope to your list of kinder tools. How are they going to understand molecular physics if they don't have an electron microscope?
In all seriousness, I'd like to add one (maybe you'll include it anyway): a magnifying glass. My sons have both learned a ton from taking their magnifying glasses outside and analyzing the bugs, the leaves and the lizard carcasses.
Would you mind tagging parts 2 and 3 as "kindergarten" so I can remember to look here when my kid is in... ahem... kindergarten? These are good ideas.
Dear Dirt.
Done.
Makes my life easier, too--if I ever figure out how to spell "kindergarten" consistently....
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