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Common Misconceptions

Nice link courtesy of Alex.

I liked this bit at the end:

"A telling comment on the issue of fairness in teaching elementary physics: Two students asked if I was going to continue asking them about things they had never studied in the class."

The answer is always this: HAHAHAHA yes.

(I am at least mostly kidding. There won't be any material on the final that we didn't cover in class, but there will be relatively simple situations that are new ... but situations which can be handled straightforwardly with what we covered in class. No surprises.)

Studying for the exam ...

I hope to have the formula sheet for the exam and the solutions to HW12 posted by mid-afternoon tomorrow (if not sooner).

Standing waves in your shower

Important application of waves.

Thursday 9 April 2009

By the way: short quiz on Thursday. It will not present a problem if you have read Ch. 16.

Really, it will be easy. Just a heads-up.

Today's bit of randomness

Physics is good for anything. Anything.

Numerical answers

Preaching to the choir.

Twitter

So, I am on the twitter (@pleclair). I was thinking lately it might be useful for posting quick updates for class, e.g., HW hints or notifications of new assignments. (Though I joined for other reasons, mainly because all the cool kids were doing it).

Would this be a useful way to disseminate small bits of course-related info?

(N.B. - it is easy to use twitter to update your facebook status and vice versa. Joining is not the time sink I thought it would be.)

Sigh.

Snipped from an article on wired.com:

Toyota's bland bar graph makes saving gas about as much fun as a physics lecture.

Sigh. Having attended my fair share of physics lectures, they do make a good point ... you can only aspire to be an occasional exception to the rule.

Final exam

Wouldn't this be fun?

Kidding. Good practice though, they are not all easy questions ... some of them do require Physics II stuff you haven't seen yet. Note 80% is considered a 'pass' by the Diesel Technician Society.

By the way: Moodle is now up to date, I spent quite a while grading over the break catching up. One thing I have noticed: the rate of missed (or partially missed) homework seems to be increasing ever so slightly lately. This is not shocking, being near the end of the term and all ... but be careful. It is not a large percentage of your grade, but the practice is crucial.

Finally: next week is the last week of advising. I am the undergraduate adviser for physics and astronomy. If you want/need to take more physics and astronomy courses, I'd be happy to talk with you about your options and give some friendly advice (that is, in addition to your regularly-scheduled advising sessions if you are not a physics major).

Theory

This loosely sums up how I feel about theory & calculations. At the end of the day, someone still has to go and look. A reality check, if nothing else.

Also, it is a thin excuse to link to XKCD. Be sure to read the mouse-over text.

Commentary.

More succinctly, and in t-shirt form.

Stupid tricks for your TI-89

A lot of you seem to have TI-89's or related instruments ... here's a nice how-to guide.

HW 5 solutions

The solutions to Homework 5 are out.

Just for 'fun,' I included code snippets in various languages to solve the last problem, in which you needed to sum the harmonic series over 75 terms. Actually, I wrote quick versions in several languages, such was the depth of my procrastination. Represented are

• C (iterative and recursive solutions)
• Pascal
  
• Perl
• LISP
  
• Python
• Java
• shell (bash) script
• Postscript
• Fortran

If you are similarly bored, how about some submissions in other languages? Or perhaps some particularly obfuscated solutions in some of the languages above?

(In particular, my postscript solution could be fancied up quite a bit for prettier output. The bash script is also a bit cheap and approximate, since one can only use integers.)

Random homework hints

9.8 Of course, you know the liquid density owing to the fact that you know the mass and volume when the can is filled. This is enough to calculate the liquid mass when the can is filled to a depth x. It is advisable to plot the resulting center of mass versus x.

9.15 You can easily find the velocity of the projectile at the top of the trajectory. At that point, apply conservation of momentum. If the falling particle has no initial velocity ...

9.45 Don't overthink this one. Conservation of momentum before and after along x and y axes. Symmetry is useful.

9.48 Both energy and momentum must be conserved, right?

Physics of the Death Star

We won't cover gravitation until just before spring break ... but file this away for later.

Another great blog full of neat physics posts, highly recommended.

This Friday's homework

By the way: typo on the homework.

Friday's problems are due at the end of the day, i.e., 1 minute before midnight, not at the beginning of class as the problem set claims.

In other news, we will begin studying work & energy tomorrow (Ch. 7). Reading Ch. 7 before class tomorrow, or at least skimming it is a Good Idea.

By the way: I tried to choose a textbook this semester that would make the reading less ... painful. I don't point out each day what you should be reading, mainly because I think it is sort of obvious from the schedule - if we start Ch. 7 tomorrow, you should read Ch. 7 for tomorrow. I am naively assuming that you do the reading each time (!), and that the more studious of you are working through the example problems on your own.

Here's a good little post on physics textbooks, FWIW. I have nearly written my own book for ph102 out of sheer frustration; the fact that I have not even thought of this for ph125 speaks to my high regard for the classic H&R text. YMMV.

Have free time?

Our IT guy over here in MINT is looking for a gopher to install software, swap out computer hardware, etc. Anyone looking for a few hours a week of work and need a little cash?