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Re: [Phys-l] Student engagement--GAIN

Not to drag this discussion on and on, but one of my favorite conceptual
"thinking" questions comes from Hewitt's book (maybe others, too). It's
the one with three balls/boxes at the top of thee frictionless hills. One
has a constant slope, one is concave, and the other convex shape. All
objects are released from rest from the same initial height without
friction.

For motion topic: Which ball gets to the bottom first and why?

Later, for energy topic: Which ball has the fastest speed at the bottom
and why?

It's really a great question because it illustrates that velocity and
acceleration are different. Few students, even my "bright" ones in honors,
every get this correct the first time around.

Physics is HOT -- Higher Order Thinking!


Forum for Physics Educators <phys-l@carnot.physics.buffalo.edu> writes:
Will have to comment here--as I couldn't disagree more--at least for
College
level courses (so we may be talking past each other).

All I want incoming student to have is a basic understanding of the
_concepts_ of velocity and acceleration--so do that with whatever works,
but
if you can't think ALGEBRAICALLY and work with the d,v,a,t equations in a
College Level, problem solving, physics course--you have no business in
that
course--or in any field that requires such a course.

It may be my background as a nuclear physicist and working for years with
low-energy (below 16 MeV) particle collisions, but momentum is most
useful
as a tool for dealing with collisions, and especially nuclear level
collisions. For that I want KE before momentum. Not interested in
coming
back to collisions later--despise the 52 chapter books now being
published!

Rick ;-)


----- Original Message -----
From: "chuck britton" <cvbritton@mac.com>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Monday, December 07, 2009 3:47 PM
Subject: Re: [Phys-l] Student engagement--GAIN


A quick note from a retired HS instructor who gained insight from a
coupla Priscilla Laws Workshops and generally was looking for better
ways to do things.

d,v,a,t equations are GARBAGE ! ! ! ! ! ! You might work up to them
eventually - but until the students have a THOROUGH understanding of
velocity time graphs. (and position time graphs too of course).
Sonic Ranger exercises are where it starts. Matching, predicting etc.

The velocity graph of straight line segments solves most 'd,v,a,t'
problems that Rick is concerned about. Finding the area of rectangles
and triangles is the analysis they need. The 'smart' ones will even
use the trapezoid area 'formula', but that's unnecessary gravy.

How many college profs are willing to lower their teaching style to
using geometry instead of the usual dvat formulas?


(Oh, and teaching momentum before KE works really well too -
but that's for another day)

Rick writes:

The only GAIN I'm interested in from pre-College courses, is that I
start
seeing some students who know some basics (say understand velocity and
acceleration)--so that we don't have to start from scratch.
_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l