## Friday, February 10, 2012

### Hysterical Physics In Motion Demo

I was rolling all over the floor watching this video, because not only is it kinda amateurish (nothing wrong with that, really), but it is hysterically funny, and they didn't intend it to be! :)

This video is a demo of the 2 Newton Laws of motion, which is fine and dandy. The demo for 1st Law (inertia) was rather clear. The object not in motion will want to stay that way unless acted upon by a force. Unfortunately, the website only describes an object that is in "uniform motion".

First Law:
Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
So the demo and the written description do not match.

The problem comes in with the demo for the 2nd and 3rd Laws. They were not very clear at all and, in fact, may have missed the mark. The 2nd Law (F=ma) was demonstrate with a hammer knocking on various objects of different masses. So year, you need more force to push on heavier mass, but how would this show the relationship between F, m, and a? It doesn't, because you can't get "a" or "F" from just looking at the demo.

The 3rd Law (action = reaction) was demonstrated with a balloon and letting the air out. The person simply blurted out in passing that the air pushes one way and the balloon pushes the other way. Huh? A "general public" person would ask "how does air pushes one way and how does the balloon pushes the other way?" It isn't clear how things are being pushed here. If anything, this is more of a demo of conservation of linear momentum.

And unfortunately, that's what the demo following this one is all about. The person started to demonstrate conservation of angular momentum, which isn't even covered. No mention of what is involved here, and no clear physics explanation was mentioned.

I'm being nit-picky here because we have seen many physics demo, even done on a shoe-string budget. I'd rather the presentation be on ONE topic (say, inertia since that was done very clearly) and the physics is explained clearly, rather than rush through a bunch of demo without any kind of details. Just simply producing a bunch of demo one after the other turns it into a circus, without any kind of useful knowledge being passed on.

Zz.