Archive for the 'Physics' Category

15
May
13

Avoiding Graphing With Calculators

As anyone required to buy a graphing calculator for pre-calculus knows, those calculators’ second-most important function was to allow their owners to play games. I can honestly say that I did almost none of this because I was a good student1 and was too cheap to buy the data transfer cable for the TI-82.  However, I was definitely fascinated by my classmates’ ability to play Pong in the back of class.  Or at lunch.  Or in the hall.

Technology has of course continued its inexorable march since the days of my TI-82 usage (circa 1998)2, and now the proud owners of the TI-83/84 series of graphing calculators can play a version of Portal in the back of class.  For the uninitiated, Portal is a gaming classic that came out in 2007 and was published by Valve after Valve hired the group of students who wrote and coded the original ‘portal’ concept in 2005.  The player controls a protagonist who is “armed” with an Aperture Science Handheld Portal Device, which is a teleportation device that allows the player to place the entrance and exit points of the teleport.  This can lead to some entertaining physics – stepping through an entrance portal on the floor with the exit on the ceiling above causes the player to fall faster and faster and faster as the player goes through the floor up to the ceiling, falls to the floor again, back up to the ceiling, etc, etc.

Anyway, all this good, clean, thought-provoking fun is available to slacking TI-83 owners everywhere thanks to the ingenuity and hard work of one Alex Marcolina (handle: Builderboy2005) at UC – Santa Cruz.  I figure Builderboy2005 is going places in the future.  In addition to figuring out how to program the game, he managed to shove a 2-D version of Portal into the 24kB3 of user available RAM in the TI-83.  That’s efficient programming.

1 Or at least I was deferential to authority.  Must be all that the fluoride in the drinking water impurifying my precious bodily fluids.
2 What, you think those graphing calculators come in handy after pre-calculus/calculus?  Hahahahahaha.  No.  Or at least you can become a physicist without ever using one.  Of course, you just graduate to more complicated crutches like Mathematica and Matlab.
3 This massive pool of RAM was only recently surpassed by a cutting-edge desktop computing device called the Radio Shack TRS-80 Model I.  In 1977.  Though you did need the optional expansion card interface to get the extra 32kB of RAM.  This thing also had the same processor as the TI-83, albeit at about a quarter of the TI-83’s blistering 6 MHz clock speed.  You have to love Texas Instruments’ business model.

16
Mar
13

Particle Physics and Boobs

So, when I first heard about the story I’m about to discuss, it was in the context of my favorite newspaper, the American Physical Society News.  I think at the time the details of the story were still in dispute and APS News tends to be about the least sensational news outlet I know1, so although I remembered some mild weirdness, it didn’t make me sit up and take notice quite like the article sent to me more recently by a friend.  In summary (though I would recommend reading the full article yourself) a notable theoretical particle physicist, Paul H. Frampton, has been sentenced to about four years in prison for (1) meeting a woman claiming to be Denise Melani on a dating website, (2) over a period of weeks being convinced that this was in fact the actual Denise Milani2 and that she was in love with him despite only communicating via Yahoo Messenger, (3) flying to La Paz, Bolivia to meet her, (4) being told that she had a last minute photo shoot in Brussels, that he could come and join her there, and ‘oh by the way could you bring this empty suitcase that I just happen to have left in La Paz’, and finally (5) being caught in the Buenos Aires airport with a suitcase full of his dirty laundry and two kilos of cocaine sewn into the lining.
Despite Dr. Frampton’s continually professing his complete ignorance of anything illegal or strange about the situation, subsequent court testimony and documents seem to indicate that he had more than an inkling of what at least might be in the suitcase.  Still, this 68 year old professor from Chapel Hill had seemingly convinced himself beyond much doubt that this glamor model was willing to drop everything, marry him, and have children with him.  He’s a bit young for dementia – after all, he was publishing papers in good scientific journals in 2011 with abstracts like

We examine models in which the dark energy density increases with time (so that the equation-of-state parameter w satisfies w < -1), but w approaches -1 asymptotically, such that there is no future singularity. We refine previous calculations to determine the conditions necessary to produce this evolution. Such models can display arbitrarily rapid expansion in the near future, leading to the destruction of all bound structures (a “little rip”). We determine observational constraints on these models and calculate the point at which the disintegration of bound structures occurs. For the same present-day value of w, a big rip with constant w disintegrates bound structures earlier than a little rip.3

He has a reputation for being a bit prickly and terribly arrogant, but these characteristics make him more likely to try and fluster some poor particle physics grad student during a conference talk rather than take on the occupation of drug mule.  The man also, by his own admission, “rarely listens to the opinion of others”, which is probably why he ignored a more worldly physicist friend who told him before he left Bolivia that he was being duped into carrying drugs.  The only thing that suggests to me that he might be a little more street smart and calculating than he appears are the facts that he had little in the way of savings, so needed money, and that the text messages he was sending to ‘Denise’ from Bolivia made specific references to his concern about drugs and drug-sniffing dogs4.
Personally, despite his conviction, I’m inclined to believe most of his side of the story.  The man certainly has a rational and penetrating mind, but one that had been cloistered and focused for decades on questions that have almost nothing to do with the world as most humans understand it.  As with any ability that is rarely or never used, his ability to interact with and read people who weren’t his peers in the academic community had clearly atrophied to the point of being nonexistent5.  As for his motivation, well, it could have been money.  To me though, his apparent complete naivete and not inconsiderable arrogance actually fits well with the story of his ‘finding love’ over the Internet with a glamor model he’d never met.  He thought of himself as a brilliant and famous physicist: a wonderful match for a famous, large-chested glamor model who was half his age.  Right.  One pubescent fantasy that was never outgrown, and so began the tragi-comedy that describes Dr. Frampton’s career change from respected professor to (perhaps unwitting) drug trafficker.  I would say something like, ‘let this be a lesson to you’, but it’s hard to come up a useful takeaway other than, “Well, sometimes people say things that aren’t true. So don’t believe everything you hear.”  Most of us, however, learn this earlier than Dr. Frampton did.  Unfortunate for him.

1 Which simultaneously explains why I enjoy reading it and why almost no one reads it.
2 An internet search will provide plenty of scantily-clad photos of this very pretty and, er, top-heavy glamor model.
3 I’ll see if I can get back to you on the meaning of that.
4 He, unsurprisingly, claims he was merely joking around with his beloved.
5 Kind of a scary thought, really.

20
Oct
12

A Bit of Automobile Physics

A couple days ago, I sat down to write a physics problem that would quantitatively illustrate the concept of power to my students.  Those of you with some physics education know that power is work done per time or the rate of consumption/expenditure of energy.  Here’s the setup:  the proud owner of a new Porsche 911 Turbo S* decides to test Porsche’s claim that the car will achieve 60 mph (~27 m/s) in a mere 3.1 seconds.  The approximate mass of the car is 1350 kg.  Determine the average power that will achieve this goal.  The problem can be done in a couple ways, but the simplest is to apply the work-energy theorem, which equates the net work done on the car to its change in kinetic energy.  Kinetic energy is 0.5*mass*velocity^2.  Go through this calculation, and the result is about 160kW or about 210 horsepower.

On the face of it, this is pretty standard introduction to physics stuff.  Nice and simple.  Illustrates how to use the new equation for power they’ve just been shown and relates it to something in the real world.  For me (and hey, maybe my students too once I talked about it**), the interesting bit is when the result is compared to the horsepower rating that Porsche gives to their engine, which is 530hp.  Now, Porsche isn’t lying.  These things can be checked, and often are.  The big difference between the two figures comes from a couple of things:  (1) Our calculation incorporates all the other forces acting on the car during its 0-60mph sprint.  Drag and contact rolling friction are forces which oppose the propulsive force delivered from the engine to the wheels, and what we’re reading out (210 hp) is the propulsion minus those energy sapping effects.  (2) 530 hp is, at least as far as I can tell, brake horsepower, which is the power that the engine delivers directly to the output shaft.  From there, bits and pieces of that power are used up by all sorts of things before it ever gets translated to the wheels.  Power steering, air conditioning, fuel pump, water pump, alternator, frictional losses in the transmission, the differential, etc, etc…all these get a piece.  All these effects combined take us from 530 hp at the engine to 210 hp “on the road” so-to-speak.

But wait, you say, that isn’t so bad!  We’re still about 40% efficient in terms of translating raw engine power to the road even with all those parasitic effects!  Indeed, that is a testament to the engineering prowess of Porsche (or any other major car company).  Of course, the real inefficiencies come from the fact that we’re using a heat engine to produce that 530hp in the first place.  I’ll write a follow-up on that subject whenever I get a little sad about heat engines not being in the curriculum*** for Physics 100 at Cal Maritime.

* If you’ve got a spare $160,000, you too could be the proud (and possibly broke) owner of this car.

** Hope springs eternal.

*** Physicist rage!!!

30
Aug
12

Back To School

Just FYI, if you’re one of the (very)* select readers of this blog, you might not have as much to read as often over the next few months.  The fall semester has begun at my place of employment, the California Maritime Academy…or Cal Maritime…or Cal State University – Maritime.  What one calls the institution seems to depend on a variety of factors.  I’m sure I’ll learn the system.  Someday.

Anyway, I try to teach physics to aspiring mariners.  They, in turn, try to learn physics from an aspiring professor.  Each of these endeavors has a varying degree of success.  In concert, however, the institution seems quite successful at training some of the people who move some 90% of the Earth’s international commerce (by volume).  If you like that fun fact, you can find many more with a bit of poking around at www.csum.edu.  One thing the website doesn’t do particularly well is highlight the location.  Vallejo the town isn’t anything too grand, but half the campus is about fifteen feet above sea level with a view of the lovely San Pablo Bay…and a ConocoPhillips refinery terminal.  Still, it is beautiful.  I’ll see if I can grab a picture tomorrow to add to this post and prove this assertion.

* extremely?