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[Phys-L] Beavis and head-butt



On 01/07/2015 12:29 PM, Bill Norwood wrote:

- Understanding this seems to be akin to understanding a living-natural
example of it - the fighting of the rams:


http://www.bing.com/videos/search?q=mountain+goat+fighting+ram

Hmmmmm. I'm not sure that's helpful for explaining the
significance of the third law. In such a situation (and
in many others), the important thing isn't the force,
it's the effect of the force.

When a bat hits a ball, the forces are equal-and-opposite,
but the effects (in the usual reference frame) are not.

When a large truck hits a small car, you could say that
"the" forces are equal and opposite, but that would miss
the big picture to a ridiculous degree. The forces on
the /occupants/ of the truck are very different from the
forces on the /occupants/ of the car!

When the rams ram each other, or when the musk oxen butt
heads, they are not trying to ascertain whether the third
law is upheld. The are trying to see who can be pushed
around and who cannot!

It is well known in the ethology literature that in the
vast majority of the cases, this doesn't involve very
much fighting. Things get ugly only when the parties
miscalculate, or when somebody is trying to move up in
the standings.

Once I was visiting my friend's farm. We hopped into
the paddock. The ram sauntered over to check me out.
He leaned his shoulder against my hip and pushed, not
real hard, not hard enough to hurt me, just enough to
see what would happen. I stood my ground and pushed
back, not real hard, just enough to demonstrate that
no, I was not going to be pushed around. He sauntered
off. He needed to know where I stood in the pecking
order, and now he knew.

She remarked that most visitors didn't know how to
do that. I said hey, I'm a D-level manager in the
research lab. I do that for a living.

Bipeds such as chickens have a pecking order. By and
large, if everybody keeps to their place, nobody gets
pecked. Interestingly enough, if you move a chicken
from one flock to another, she always starts at the
bottom. If she wants to move up, she has to peck
everybody along the way.

Classic reference:
Konrad Lorenz
_Foundations of Ethology_

Other bipeds also play chicken games, only they are
much stupider about it:
https://www.youtube.com/watch?v=u7hZ9jKrwvo
https://www.youtube.com/watch?v=KQbCLI49nAI
https://www.youtube.com/watch?v=O5hV2b8o1ls

The only thing stupider than that is provoking a fight
when you know in advance that the other guy is not
going to back down. Remember, the whole point of the
exercise is to see who can be pushed around and who
can't. So if you already know that, there's nothing
to be gained. As an example of what I'm talking
about: the recent government shutdown.

One more example: Consider the lead-up to WWII.
Germany started out utterly defenseless in accordance
with the Versailles treaty. Hitler made a series of
small moves to see who could be pushed around and who
could not. A lot of people on both sides understood
this for what it was. Canaris understood. Churchill
understood. Neville Chamberlain did not. Churchill
was spectacularly wrong about a lot of things (Gandhi,
Gallipoli, etc.) but he was right about Hitler. Early
on, there were several critical points where if somebody
had pushed back, Hitler would have had to back down
without much of a fight.

===================================

Getting back to force-pairs: All too often, we are
inconsistent in a way that is grossly unfair to students:
a) In connection with the Hewitt CONCEPT CHECK we ask
students to recognize that it is a stupid question and
instead /answer the question that should have been asked/.
b) On the FCI and FMCE, we ask what is basically a stupid
question about the forces themselves, forces that cannot
be measured operationally, all while paying no attention
to the effect of the forces (which could be a matter of
life and death) -- and yet we expect the students to take
the question at face value, according to some narrow and
highly technical definition of "force".

Take your choice: You can play by rule-set (a) or rule-
set (b), but not both.