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Re: [Phys-L] The Make-Believe World of Real World Physics



I can certainly envision lots of students claiming the acceleration at the peak is zero. However, i think this answer comes from students trying to memorize physics points rather than think about and analyze physics. In my experience, students that answer a=0 remember there is something unique about the top. They remember something is zero and they go with a =0 since we are asking them about a.
If we ask them if there velocity at the peak will remain constant, few will say /yes the velocity will be 0 and will stay 0 at the top forever and the ball will never fall/.
Our challenge is to get them to analyze the scenario and avoid the temptation to answer reflexively.
In my opinion, that is the challenge w a lot of the challenging and trick/tricky physics questions students encounter in their first course.

Have a good one.
Paul.

.:. Sent from a touchscreen .:.
Paul Lulai




-------- Original message --------
From: Kirk Bailey <kirkbaile@gmail.com>
Date: 07/29/2013 5:01 PM (GMT-06:00)
To: Phys-L@phys-l.org
Subject: Re: [Phys-L] The Make-Believe World of Real World Physics


I can't remember where or when, but I know I read that the number one
misconception (based on how many students still missed it at the end of the
course) was the acceleration of an object thrown straight up at the peak of
its trajectory. Just understanding that it isn't zero at the top is a
non-trivial objective, and I don't see it as an easy question in any
student universe.


On Mon, Jul 29, 2013 at 4:19 PM, Anthony Lapinski
<Anthony_Lapinski@pds.org>wrote:

Right. And a student in a physics class should answer it differently
(correctly). Acceleration = rate of change of velocity = gravity =
constant (in free fall).

Unless, of course, I am missing something or in a different universe.


Phys-L@Phys-L.org writes:
Folks on the street indeed are likely to think of acceleration = speeding
up and deceleration = slowing down. therefore acc at top = zero.

Every beginning physics student should be able to think of the velocity
graph with it's slope and areas included.

On Jul 29, 2013, at 3:36 PM, John Denker <jsd@av8n.com> wrote:

You might be a redneck physicist if you buy 48 cans of
Big Flats beer and cool them off using liquid nitrogen.


On 07/29/2013 07:29 AM, William Maddox wrote:
In this universe the acceleration of a ball at peak question would
not be considered ill posed in the context of a physics test
following chapters on projectile motion and gravity.

Congratulations on living in such a nice universe (A).

Meanwhile, there are plenty of people on this list who
live in a different universe (B), where students find
this question hard or at least counterintuitive.

I reckon this list is extremely valuable, because it allows
us to recognize and discuss the difference between these
two universes.
-- Why is this an easy question in one universe but not the other?
-- Can we move everybody from universe (B) to universe (A)?
-- If so, how?

I remind everybody yet again that many things that seem
hard at the beginning of the road seem easy (and are easy)
at the end of the road.

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

Physicists tend to write as little as they feel necessary.

... which can be a big part of the problem, if they misjudge
what is "necessary". This is known to be a problem whenever
experts are talking to non-experts, including students.
Miscommunication makes things hard, even things that ideally
"should" not be hard.
_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l


_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l




--
Kirk Bailey
Never use a big word if a diminutive synonym is as efficacious.
_______________________________________________
Forum for Physics Educators
Phys-l@phys-l.org
http://www.phys-l.org/mailman/listinfo/phys-l