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Re: [Phys-L] Physics, Errors and Differenet Teaching Styles

Regarding /real hs physics courses/, it is up to the instructor to put the course content within a useful context. The only thing stopping a high school physics teacher from adding these questions is time, and the idea of the question type. The ap physics c - mechanics course leaves plenty of time for questions like these to be added into a year long class. If one does ap physics C-mechanics as a semester class, then time would certainly be an issue.
Have a good one.


Paul Lulai
St Anthony Village Senior High

----- Reply message -----
From: "chuck britton" <cvbritton@mac.com>
Date: Wed, Jun 27, 2012 9:33 am
Subject: [Phys-L] Physics, Errors and Differenet Teaching Styles
To: "Phys-L@Phys-L.org" <Phys-L@Phys-L.org>

A barge loaded with a stack of steel plates is approaching a low bridge.

Would their clearance be helped or hindered by tossing a plate or two
overboard?

(It's a river/canal, not a closed swimming pool/lake.)

explain your reasoning.


It really IS a shame that 'Real HS Physics' (by this I mean the AP-C
curriculum) totally leaves out so much of the important good stuff.

We sent a VERY intelligent, advanced student off to MIT, but he
couldn't predict/explain how a He balloon would behave in an
accelerating van. His excellent math skills let him argue EITHER side
of the discussion. When asked for a Force Diagram he could only come
up with the 'Buoyant' force with no idea of the pressure thing.

Later he was fascinated by the pressure area integral relating to the
weight volume integral.
He had the math tools (Cal-3) - just not the intro ideas.
.
At 1:18 PM +0000 6/27/12, Philip Keller wrote:
>
On 6/26/2012 6:15 PM, Jeffrey Schnick wrote:
>> #3. "A boat carrying a large rock Is floating on a lake.
The boulder
>> is thrown overboard and sinks. The water level in the lake (with
>> respect to the
>> shore)
>>
>> 1) rises
>>
>> 2) drops
>>
>> 3) remains same"


My favorite solution to this old puzzle said it this way: while on
the boat, the boulder displaces an amount of water equal to it in
weight. Thrown overboard, the boulder now displaces water equal to
it in volume. Since the boulder is denser than water, we know that
the first volume is bigger. So it displaces less water submerged
than when it was in the boat.

One advantage of this solution is that it doesn't depend on the
normal force from the lake bottom. After all, the water level drops
even before the boulder reaches the bottom.

Also, this solution method handles a common variation on the
problem: throwing wooden blocks overboard instead. Now, they
continue to displace a volume equal to their weight, so no change in
water level.
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_______________________________________________
Forum for Physics Educators
Phys-l@mail.phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l