Re: [Phys-l] Good Questions

["Cliff Parker" <cparker@charter.net>]

> Here's a simple one:
>
> Suppose you are sitting on the bottom of an ordinary swimming pool, 
> several
> feet below the surface.  You have an ordinary hose that leads to open air 
> at
> the surface.  You breathe in through the hose, and breathe out bubbles (to
> ensure that the hose doesn't fill up with exhaled air).
>
> This scheme is not widely used.  Why not?

Yes this is more like what I had in mind.  Unfortunately it is one that I 
also use each year.  I am looking for things that everybody or at least 
nearly everybody has some familiarity with when they walk in the door. 
Everybody has seen contrails and wondered what's going on there.  I think 
just about everyone has wondered why they couldn't breath through a hose 
from the bottom of a pool.  I want things that my students have seen perhaps 
many times and never thought they could figure out but with the opportunity 
to give it some thought and discussion with classmates and teacher they will 
learn they can figure it out.  I want them to do what I (we) all do so 
often.  Ponder a question and develop a sure understanding of an answer 
without having to check with an expert for verification.

What is a contrail made from and why is it there?
How does siphoning work?
Why does it rain when we have low atmospheric pressure?
What causes the phases of the moon?
What causes the seasons?
Why can't I sit at the bottom of a pool and breath through a hose?
What causes the tides?