Friday, December 25, 2009

Uncertain Christmas Gift

At first, this gift was in a mixed state.

It was clearly a book, and the odds favored it being a particular book, but could we know for sure without opening it?

Ah, now we know for sure ...

It is a GREAT book!

Notes added to correct a major oversight -

Link to the How to teach physics to your dog book web site. (Chad gets an extra cut if orders go through there.)

Here are the two semi-famous blogs that started it all:

Those stories are the basis for two of the chapters. Each chapter starts with a dialog with Emmy, followed by an elaboration on the science behind that idea.

Chad deserves major kudos in my view for including a final chapter that debunks much of the junk that has been written based on pseudo-quantum non-science.

Other material can be found in Chad's general category of Physics with Emmy, but that is mostly about writing (including the story of how he got the book contract) and promoting the book. So you don't have to dig through all of that for the best bits, here is the link to one that includes the slides from a talk he gave, and two movies that deserve special mention: The Bohr-Einstein Debate (with puppets) should not be watched while drinking coffee. The choice of character actors is, shall we say, priceless. But it is not just whimsy. As a long-time student of those discussions and owner of a personal library of some of the key books, I think Chad did a very good job selecting what belongs in his little play.

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Thursday, December 24, 2009

It is almost Christmas ...

... and it's not really Christmas until we hear dogs barking "Jingle Bells".

It was a sure sign of the approaching holiday when J. P. McCarthy would play that song on WJR.

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Tuesday, December 22, 2009

Merry Christmas and a Happy New Bank!

Bank failures continue. Every week (usually on Friday), the FDIC moves in and takes over a few more failing banks. Most are in trouble because of bad commercial loans. There was one striking example locally where an investor group led by a Realtor bought a 5 million dollar property and couldn't even pay the taxes on it from the rents. It sold for less than half that in foreclosure. Although the bank that lost about three million dollars on that one loan was not in this state, some local banks have made similarly bad decisions.

[Memo to the right wingnuts: There has been no change in the law regarding loans to poor people to encourage home ownership, yet the banks have tightened up their lending practices. That is what mathematicians call a counterexample to the claim that politics rather than greed caused lenders to loan money without checking anything. Another counter example would be where a Swiss bank nagged an owner into refinancing a now-bankrupt resort so they could earn the origination fee.]

So how can you tell if your bank is over extended? How can you find out how many toxic loans it has, or how many bank-owned properties it owns? Easy:

An MSNBC story provided a nice, color coded map showing the extent of the problem on a state-by-state basis with links to a separate "bank tracker" site. The main article only does banks, but if you go to the main site you can choose (top of the left column) to look for banks or credit unions as well as their methodology and who has obtained TARP funding.

It is worth a look, although you do have to know where your bank has its headquarters.

What I like is that they show the time dependence of the bad assest ratio in a bar graph, so you can see the trend as well as the raw numbers in a table. For perspective, the reason their bar graphs don't max out when a bank gets to a 100% ratio between troubled assets and capital plus reserves is that the ones that have been taken over can be in the 300% to 600% territory. However, that is not the only metric. I saw one bank where the ratio was just over 100% but they had been losing over a hundred million dollars a quarter for a year.

I was glad to see that our banks and our credit union are in reasonable shape. One has a ratio around 40%, but it has been stable for most of the year and they are still making a profit. Not so for another local bank, which has advertised how helpful it is to local businesses. Their ratio has been going up by leaps and bounds, hitting 100% last quarter along with a large negative profit. I wouldn't buy any stock in that one!

And always remember: the cap on FDIC insurance applies to the sum of all of the accounts in your name, not each account.

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Lazy American Students?

There is an interesting "quick take" in IHE today asking the rhetorical question Do American Students Bring Down the Curve? based on an opinion column in The Boston Globe that answers it in the affirmative.

First, it is important to realize that this is the opinion of one instructor, and even she does not claim that all low grades go to Americans (which make up 80% of the undergrad population at her private business college) or that none of the A grades go to Americans. But, from where I teach (at a CC), I think she has it all wrong. She has a problem with Snowflakes, not Americans. Let us start with where she teaches, then look at what she might not be doing where she teaches.

The college:

She teaches at Babson College. Yeah, I had to look it up, although I suspect Bostonians would be aware of it. This is a small (the entire freshman class of 471 would fit easily in one half of the dorm I lived in at Enormous State University, with space enough for half to have private rooms) expensive private college ($37,824 for tuition plus $12,500 for room and board) that is basically devoted to business majors. [Aside: that room and board rate is almost twice what it is at Enormous State, so they probably do all have private rooms.]

They look selective (471 enroll out of 4100 applications), but their middle-50 on the SAT (1830 to 2070, meaning 610 to 690 on each part) puts about a quarter of their freshman class below the "aptitude" of most of my 2nd year CC students and in a range where we would likely be requiring remedial math or english classes. A bit over 20% are international students.

(These details are from their official facts page. Purely by accident, I saw an article in a November "Business Week" that ranked them highly for custom executive business education programs.)

Definitely "snowflake" territory. Many of the American students are probably Wannabe Trumps with well off (if not wealthy) parents and got by with minimal effort in suburban schools where you get a bonus point toward your GPA just for taking what is called an honors class. [Schools where a 4.0 is the new 3.0 average.] In that environment, the mere fact that the college gives out C, D, and F grades in a freshman composition or history class is probably a shock. I'll admit that I am shocked that grades like that are tolerated by a student-centered retention program where one mid-year drop out costs the college $25,000!

To continue my generalization, they have probably never had to work for a living, and might never have held a job. They know they want to be business men or women, but don't know what skills are used on the job.

I can definitely see how one tail of the distribution in her class might be made up of the 25% who combine mediocre skills from high school with poor motivation.

The teaching:

My thoughts here are driven by an observation I posted just the other day on FSP's blog in a discussion about why tenured professors should care about what is in student evaluations of teaching. My comment concerned a favorite student observation of decades past: An engineering major stated that ze hated physics and couldn't understand why ze had to take it. What did I learn? That one thing I need to teach real early in the course is why it is required for engineering majors! Turns out lots of them don't know why because they don't know what engineers actually do. This student probably would believe that something taught in an engineering class was relevant to a career, but didn't get the concept of prerequisites so everything else was just a speed bump that got in the way of what they thought they needed to study.

I'd be willing to guess that the problem is even bigger with rhetoric classes. Now Babson College knows it is relevant, but do the students?

Here is a key remark from Babson's About page that might put this in perspective:

The undergraduate curriculum integrates core competencies, key business disciplines, and the liberal arts into foundation, intermediate, and advanced-level courses. The competencies are rhetoric; quantitative and information analysis; entrepreneurial and creative thinking; ethics and social responsibility; global and multicultural perspectives; and leadership and teamwork; and critical and integrative thinking.

Notice that reference to "rhetoric", the subject taught by the author of this opinion piece?

[Side comment: I like the word FOUNDATION as a synonym for prerequisite, although I'll stick with BASIC for some of my applications. It sends the right message for engineering, in particular.]

I would hope something this basic to the learning goals of the college was part of their orientation. Of course, if those kids were busy updating Facebook (which might rival drinking as a reason for failing out of college) during orientation, they might have missed it so it needs to be said in every class, and not just on the first day. "Today we are working on the foundation for the report-writing skills refined in Business 301, skills that will get you that first big promotion." And I would hope that the teachers in their freshman business class refer to the importance of rhetoric just as I point to specific math skills they will learn later on and apply (along with physics) in more advanced engineering classes.

We all have to signal the importance of the whole of what they are learning if we expect them to retain the parts that really matter.

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Monday, December 21, 2009

Happy Solstice!

I've been pretty silent here, so should interject something.

The solstice this year was just after mid day, so the sun was at its highest point when it reached its lowest point (relatively speaking) in the southern sky.

Elsewhere ...

The topic of teaching evaluations and improving teaching at Female Science Prof's blog might be a jumping off point, but I'm not quite ready for spring semester yet. When I am, I might also pick up a few other loose threads, like math education.

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Saturday, December 5, 2009

Torque and Angular Momentum

Rhett Allain has a very nice blog post about angular momentum featuring the precession of a bicycle-wheel gyroscope that he demonstrates here:

I find wearing a long-sleeve shirt with shorts to be an interesting touch.

In addition to my comment on his blog, I'll add the following about how I introduce it in my classes:

Based on experience as a student and an instructor, I think it is usually best to present the prediction before doing the experiment. However, in this case I generally interleave the two.

As with most intro textbooks, mine packages angular momentum along with the cross product definition of torque in its own section so it is easy to omit completely. I integrate tau=rxF into my initial introduction of torque and the various ways of calculating it, but then stick with tau = I*alpha until I get to L.

As soon as I introduce L, I go into the generalized second law as tau = dL/dt (pretty much the way we jump from F = ma to F = dp/dt once momentum is defined). After connecting this to tau = I*alpha, I then ask "So don't you wonder if that cross product in the definition of torque is real? Is torque really perpendicular to the force?".

Then I do the demo, quickly, just enough to see the rotation.

WTF? At this point I do the detailed calculation, exactly as shown in Rhett's blog, and then REPEAT the demo. This time, however, I slip an "L" arrow onto the handle so they can see it precess.

What if I hold it by the opposite handle? What is tau now? Aha, it goes the other way!

What if L = 0? Ah, so "falling" is actually rotation in this case.

... and finally ...

What force keeps the center of mass from falling with L is not zero?

The string! Now if I could only measure the force on the string during the demo with L not zero and compare it to the force when L is zero ....

But to summarize: In this case I think they need to see a taste of the phenomenon to understand why I would bother with such a detailed calculation. It also means that I end up doing the demo itself several times, and I use the wheel with the L arrow on it when doing the drawings, since they are not yet experienced at getting a 3-D image out of two projective views. Few have had a drafting class or Calc III.

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