Re: arons and dry ice

[Justin Parke <FIZIX29@AOL.COM>]

In a message dated 10/8/2002 7:43:38 PM Eastern Daylight Time,
cparker@CHARTER.NET writes:


> No need for a 50 pound chuck of dry ice or glass.  Any size chuck will do.
> Something about the size of your computer mouse works well.  Place it on top
> of a demonstration table or tile floor if that's all you have.  Make sure
> the surface is as clean as you can get it.  Let the chuck sit for a few
> minutes until the bottom surface of the ice becomes flat.  Then just give it
> a scoot.  Extension - take a wet paper towel and wipe some moisture on the
> table top then slide the dry ice over the moisture.  Cool smoke! Extension
> 2 - put a chuck of dry ice on an aluminum chalk tray or other metal surface.
> Press down with a stick or while wearing a glove.  It will screech and
> holler like you wouldn't believe.  Have fun.
>
> Cliff Parker

I think one of the benefits of a large chunk is the opportunity for the
students to interact with a lot of inertia.  Arons was citing the
"preconception" that a force is to be equated strictly with an impulse, but
an impulse will be insufficient to stop a 50 lb chunk and the students will
be forced (no pun intended) to push for a longer period of time.  Then they
realize that a force can be exerted over a period of time, and that when the
force is no longer being exerted, it *no longer has an effect*.  A small
chunk may reinforce their preconception, but OTOH it may be all I can
reasonably do.

Thanks for the feedback

Justin

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.