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Re: [Phys-L] Sequence

I dont believe there is research that has checked every starting point. I was certainly taking some liberties with that statement. Is there research that states kinematics the best place to start? I doubt it.

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

-------- Original message --------
From: Larry Smith
Date:03/19/2014 9:35 PM (GMT-06:00)
Subject: Re: [Phys-L] Sequence

I certainly understand (and sympathize with) "you can start anywhere you want," but the real way to answer this question is through physics education research. Does the research say it is equally good to start anywhere you want?


On Mar 19, 2014, at 7:02 PM, Paul Lulai wrote:

You can start anywhere you want. What changes is the depth the related content is understood at that time and what we hand wave about at that time.
We are so used to kinematics first that we forget that students are discussing constant velocity but have "no physics understanding"* of why the thing goes at a constant velocity. We follow that with acceleration and the kids have "no physics understanding"* of why the thing accelerates. We teachers / instructors are fine with that because that is what we are used to.
Switching it to Energy First, Forces First, Momentum First, Circuits First, just changes where the hand waving is. Right now we hand wave over the discussion of net force = 0 for constant V and net force = constant for constant a.

Force first and we can hand wave over velocity a bit, but still hit, "what happens to its speed?

I don't do forces first, but I can see a real advantage to starting out with Forces in equilibrium. Structures with Fnet=0 dont change velocity.
How do you measure force? with a scale. What are their units? N or lbs. It says so on the scale. What is a Newton? It is a 1/4 pound. Go to McD's and order a Newton Burger.
All set for forces.

I don't remember who mentioned it, but I really like starting with Newton's third law. We use N3L in TONS & TONS of free body diagrams but hand wave through it.
Why does the car go forward, the person able to walk, the helicopter able to hover, the airplane able to move forward... We use generic terms like thrust. In my opinion, that is missing a HUGE spot to grow their understanding of physics. Do N3L first, and all the fbd can actually be pretty acurate and fictionless (no R).

Have a good one.

*no physics understanding because some kids will feel they know what is going on, but they usually are the prior-conceptions that need to be cleaned up.
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