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Re: [Phys-l] FW: universal gravitation lab



On 02/06/2007 08:55 AM, White, Pat wrote:
I am looking for a universal gravitation lab. I am high school physics teacher and I do have
interactive physics on 30 computers I would love to do something on this system if it is out
there.

First, a message from the keen-grasp-of-the-obvious department:
The key criteria here are
-- universal gravitation
-- high school
-- actual lab work

Pick any two of the three. The magnitude of G is too small, on the
usual laboratory scale, to accommodate all three criteria at once.

I have nothing against computer activities (see below!) but as a
point of terminology, I'm not sure they ought to be called "lab"
work in physics.


I'm not sure what is meant by "interactive physics" in this context;
there are various different creatures that go by that name. If
you're talking about this:
http://phet.colorado.edu/web-pages/whatsnew.htm
then there are already "solar system" and "lunar lander"
simulations available. Those have quite a lot of relevance to
universal gravitation.

I haven't checked to see how fancy that particular "lunar lander" thing
is, but if you can find (or make) something that comes anywhere near the
full Apollo mission profile, that is a tour-de-force that requires real
understanding of the law of universal gravitation (and some other physics
besides):
-- launch into circular low-earth orbit
(Hint: launching /up/ doesn't do the job.)
-- figure-8 transfer orbit
-- lunar orbit insertion burn
-- descent and landing of the LM
-- ascent into lunar orbit
-- rendezvous (!) and docking in lunar orbit
-- return transfer orbit that leads to a nonfatal reentry corridor.

Just the idea of rendezvous in orbit is quite something; NASA got it
wrong the first time
http://en.wikipedia.org/wiki/Gemini_4
Reportedly the Soviets got it wrong more than once; they didn't learn
the lesson of their first failed rendezvous mission. How embarrassing
is that?

It's easier to simulate this than to explain it ... in particular to
explain it well enough that the rendezvous strategy seems non-paradoxical
and non-inconsistent with what Muggles know about F=ma. It /can/ be
explained, but the teacher had better be well prepared.

There is an opportunity for some solid motivation here: "The best
engineers in the world got this wrong. Having learned from their
mistake, we can get it right, and understand the right answer in
terms of physics."

According to some accounts, the first computer game in the history of
the world was a Lunar Lander simulation.