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



There are mistakes in all physics books, including Hewitt's. I feel Hewitt
is more readable than most other physics texts. Seems like physics to me...

I disagree that physics concepts are simple. They are not! Try to explain
velocity and acceleration to students. Throw in some graphs, and it
complicate matters. Roll a ball down a ramp and ask the kids when the
instantaneous speed equals its average speed for the entire trip. Even my
brightest students miss this one. This is difficult! Then do the three
hill problem (from Hewitt), with a constant slope, concave, and convex
hills. Which ball makes it to the bottom first? Few get this correct.
Still, it's an interesting question to show that velocity an acceleration
are different. And they are hard to understand!

And these are the "easy" concepts in physics. Newton's Laws (and other
concepts) are way more challenging and counterintuitive. This has been my
experience teaching students for nearly 25 years...

We need engaging teachers. Make it interesting, relevant, and (hopefully)
fun. Books (passive) are almost unnecessary and irrelevant. We need to
focus on what goes on in the classroom.


Phys-L@Phys-L.org writes:
Imagine hiring a metal-working machinist to fabricate a complicated
part. Would you rather have a machinist with skill but no tools,
or tools but no skill?

I consider that to be a silly question. The machinist needs both
skill and tools to get the job done.


On 07/11/2013 11:34 AM, Anthony Lapinski wrote:
Imagine teaching a physics class with mostly concepts and little/no
math.
Now imagine teaching a physics class with mostly math and few
concepts/demos. I wonder how students would react to these. What would
they like more? What would they look forward to more? What would they
share with their family at home?

Please please don't formulate the question that way. Just because
option (a) is no good does *not* prove that option (b) is any good.
Manichean multiple-guess reasoning rots the brain.

Physics requires both concepts /and/ formalism (including math).
It covers an area in the plane, with concepts along one axis and
formalism along the other axis. If you fixate on one axis or the
other, you cover zero percent of the area.

You need the physics in order to motivate the math, and you need
the math in order to explain the physics. At this point I do the
itsy-bitsy-spider thing with my hands.
http://www.youtube.com/watch?v=eiWbjoOOly4&t=0m55s

I like the Hewitt approach (and his books have little/no math)

Parts of that book are carefully thought out, but many other parts
are just pathetic. Mostly it emphasizes rote regurgitation to the
near exclusion of reasoning.

The overall result is to present something that is completely useless.
I don't know what it is, but it's not physics.

Physics concepts are simple. Because they are so simple, they are
useless unless they can be /combined/ with other concepts, combined
into long /chains/ of reasoning. Hewitt fails to do this.

For example: In section 38.4 it emphasizes that «Light behaves like
waves when it travels in empty space, and like particles when it interacts
with solid matter.»
A few sentences later we find «CONCEPT CHECK: What causes light to
behave like a wave? Like a particle?»

I’m sorry, but that is not a check of the concept. That is only a check
for rote regurgitation of the words that appear higher up the page. If
you wanted to check the concept, you would ask the student to apply the
concept in some setting different from the original setting.

The fact that Hewitt is completely wrong about the distinction between
waves and particles just rubs salt into the wound. This, by the way,
is one of the eleventeen things that makes rote learning dangerous:
Rote can be used to learn wrong things just as easily as right things.

I used to think that "Conceptual Physics" was a euphemism for "Bonehead
Physics" but even that is too generous. Whatever it is, it's not physics.

http://www.av8n.com/physics/hewitt.htm

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