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# Re: [Phys-L] kinematics objectives

• From: Bill Nettles <bnettles@uu.edu>
• Date: Thu, 9 May 2013 20:43:50 -0500

I have demonstration in which I "prove" that Aristotle is right about heavier objects falling faster. I have three squares 10 cm x 10cm: one of cardboard, one of aluminum and one of lead. I drop them in pairs, flat side facing the ground. Lead wins every time. You have to drop from about 2.5 meters to make it obvious that it hits before the aluminum. Then we talk about air resistance, shape profiles, and a_air=F_air/m so that the more massive object has less acceleration upward due to air. Then I take two sheets of paper, let them both drift to the floor, then crumple one and release them again.

I've tried dropping the squares with the edges facing down, but the cardboard flips too easily.

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Philip Keller
Sent: Thursday, May 09, 2013 5:07 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] kinematics objectives

JD wrote:

By telling students their ideas are not crazy wrong, just /restricted/, they are
less likely to get defensive.

------

That made me remember something from one of my first years teaching. I
was presenting some of what Aristotle had to say about motion as in
introduction to Newton's laws. I was about 10 minutes in when one of my
students raised his hand to interrupt: "Wait. Are you saying that this stuff is
WRONG?" I said it was...and he said "but this is the first thing you've said all
year that I understand!"

Ever since then, I have made it a point to acknowledge that it is completely
reasonable to believe that the natural state of an object is to be at rest. If
you had to use your personal experience to choose between Galileo and
Aristotle, Aristotle would win.

Similarly, it is just as reasonable to believe that the Sun goes around the Earth
as do the stars. Aristotle was not a dumb guy. Neither were those ancient
Greeks.
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