General Physics Exam

Question:

If the law were changed so that traffic in Great Britain travelled on the right-hand side of the road instead of on the left, would the length of the day increase, decrease or be unaltered? Explain the reasoning behind your answer.

Answer:

It would be unaltered.

Driving in the opposite direction to the Earth's rotation may have some effect due to the conservation of angular momentum, but roads in Britain go in many directions, so the effect would cancel out.

When the driving in the opposite direction to the Earth's rotation, angular momentum is required, so when the car starts a small fraction is "robbed" from the planet. However, this will be returned as soon as the car stops - in fact, it is necessary if the car is to stop thanks to the conservation of angular momentum. Friction takes care of the stopping (and hence the return of momentum) for you.

Even if we assume that people drive in the opposite direction, and do not stop, sooner or later they are going to give in and come home. Probably they will do this before completing half a circuit of the Earth's circumference (after all, we're only looking at Britain), so it will make the most sense to come back the way they came. Travelling in the opposite direction will also return the momentum to the Earth.

If we ignore all this, and pretend that either stopping, returning, or other cars moving in other directions does not lead to a cancelling out of the removal of angular momentum, we still encounter a problem. The Earth is huge, your car is not. The effect of a car's momentum being gained from the Earth would be so minor that it would likely not be measurable, since the mass of the Earth is so much greater. So, since the difference between the mass of the car and the mass of the Earth is so great, the change in the length of the day would be negligible.

That is, unless your mum is driving the car. Fortunately, she's too stupid to drive.

I thank you.

Addict

My Amazon recommended list under "Books":

-Concepts in Thermal Physics - Stephen J. Blundell

-A First Course in General Relativity - Bernard Schutz

-Introduction to Elementary Particles - David Griffiths

-An Introduction to Modern Cosmology, 2nd Edition - Andrew Liddle

-Schaum's Outline of Optics - Eugene Hecht

-Lectures on Quantum Mechanics - Paul A. M. Dirac

-'What Do You Care What Other People Think?': Further Adventures of a Curious Character - Richard P. Feynman

-The Pleasure of Finding Things Out - Richard P. Feynman

-The Character of Physical Law - Richard P. Feynman

-Atomic Physics - D. C. G. Jones

-The Meaning of it All - Richard P. Feynman

-Mathematical Techniques: An Introduction for the Engineering, Physical, and Mathematical Sciences - Dominic Jordan

-Introduction to Fourier Optics - Joseph W. Goodman

-Particle Physics - Brian Martin

-An Introduction to the Physics of Nuclei and Particles - Richard Dunlap

That isn't edited, that's just the first 15 books (i.e. the first page of recommendations) that comes up. I'm willing to accept that I may have a problem - but I dispute any suggestion that I have some kind of Feynman addiction. I only own the 2nd volume of his lectures and his Easy and Not so Easy Pieces (not including the rest of the lectures on audio-book, or the copy of Surely You Must be Joking Mr Feynman that I picked up for the physics society library)

I just ordered a physics text book from amazon - hence noticing my recommendations. Principles of Optics by Born and Wolf if you must know. I ordered it because it was recommended as being useful for my project (which is on solid state physics, not optics, but nevermind). I don't have a copy, the society's library doesn't have a copy, the main library has three - but the only one available for long-term loan won't be back 'til November and I've never been cruel enough to request books back. Ordering it was my only option.

That's how it happens.That's how you wind up in a situation where you have more books for your course than you have books of any other kind - including fiction. It starts by getting the main recommended text for each course. Next you pick up any other text mentioned more than once because "it might be useful to have alternative explanation." After that you'll buy anything recommended at all, provided you can find a copy for under £10. Before you know it you're acquiring books by accident and you're running out of shelf-space.

Add this to the fact that I'm acting as the society's librarian this term - giving me full and constant access to the library - and I'm still buying books, and you'll understand the gravity of the situation.

I am an addict. I am ready to admit that. At least it's not crack.

Empress

A little over a month ago I was appointed President of PhySoc (the Glasgow Uni physics society). Naturally enough I was most pleased, and have decided to set about abusing my powers as soon as possible.

So far, among other things, it has been agreed that the title "President" will be changed to "Empress." I'm happy with this, but it does make me think I ought to start and "empire" of sorts. Control of a single society may not be enough. I intend to start by controlling AstroSoc (the astronomy) from the inside, until such as point as they are ready to call me their leader.

So, I have made sure everyone on their board agrees with me on important points, and I have appointed Martin the position of AstroSoc Rep within my board. Although, clearly a better title would be AstroSoc spy. If there was anything interesting to spy on them for.

I can only be president for one year, which alarms me. So once the year is through I intend to give someone else (of my choosing, none of this silly voting business) the title of "President." I shall continue as Empress, simply telling people that it's a largely meaningless role, and that I'm really just there to help out.

Of course, the "President" will be nothing more than a puppet, happy to do exactly what I suggest.

We are currently working on a greeting that makes me look slightly less like Hitler, and a"goodbye" that makes me look slightly less like a trekkie. But, you know what, I'm working with physicists here, these problems were always bound to show up.

In addition to this, I've decided that I get 10 votes for each member of my committee, and I'm going to install a lion pit in the Kelvin Building (to throw people who irritate me into).

I'd make an excellent dictator. I've even told you my evil plans before I'm certain there's no way you'll survive. They'll make a Hollywood movie about me one day, but only if I give them permission to do so.

Geeking Out

Some of you may already know this, but I'm now ready to share this with the world. I know a lot of people may be prejudice against me for this, and I understand your discomfort around me, I only hope you can find it in yourselves to treat me no differently, I'm still who I always was, just with this as well. I'm not going to go so far as to campaign for rights for people like me, I don't really feel that we suffer as much as we once did.

Anyway, I'm ready to admit the truth at last, I hope you won't reject me. Here goes;

I'm a geek.

I first realized years ago, in high-school. I knew I was different from the others, I liked science better than art, and actually enjoyed learning in general. People used to tease me for being "a swot" and for consistently getting good grades, which I liked and got a kick out of - everyone else seemed embarrassed if they got anything greater than a C grade. As if success was wrong.

I didn't enjoy sport, at least until we started studying the effects and benefits of exercise on the body. No one else could understand why we should be studying biology in P.E. or games, but for me it finally made it interesting, and I was finally curious enough to start genuinely taking part - after which I was regularly asked to join the netball team or the gymnastic team, but I still held grudges with those who teased me for my IQ, and had no interest in associating with them outside of the competitions - which would have been necessary.

I was interested in home economics classes, which were mostly made up of cooking, I wanted to try new foods and play with different flavours, cooking times and combinations, wanting to be able to prepare something more intriguing than fish-fingers with chips and peas. While the other students balked at trying cheeses more extravagant than cheddar, and were positively horrified by produce from other countries, I was already preparing meals from countries they couldn't even find on the map.

For a while I tried to hide the truth. I didn't use my advanced lexicon, or tell people I knew things because I liked reading books or watching documentaries. I asked my sister to tell me what was happening in soaps and reality tv, so that I didn't have to stomach watching them in order to keep up. If people asked me what I did at the weekend, I'd say I went out with friends, went shopping, watched tv - the truth was I'd play video games, read, or tinker with microscopes and chemistry sets.

Eventually I gave up, and allowed people to think what they wanted. I went to sixth-form to study phsyics, maths and chemistry, and then applied to University to study physics.

This Christmas, I'm most pleased with my new NAS drive (although I admit that until asking M's advice, I had no idea that they even existed - thanks M, you're a greater geek than I'll ever be). I also love my geeky tshirts, and all the books I recieved, especially my new copy of The Science of Discworld, which nicely combines two of my favourite things.

So, I'm sorry I'm different, but I am. This is what I love. I'll be spending my Christmas break in bliss - since I don't have exams to study for, and my boss has mysteriously disapeared - I'll be tawling wikipedia, learning Russian, playing with my NAS Drive, reading about science, playing old videogames, thinking up get rich quick schemes, learning about robotics, finding interesting music and generally geeking out. Reality TV won't be on my scedule, nor will gossip magazines or chart music.

One day the geeks will rule the world, mark my words. Join us, we've got robots, and sometimes we go to Space!

Breaking the Laws

A couple of days ago I got a text from my mother, asking me when I'd be home because she'd quite like to call me. I said I was home now, which was true, and was asked why I wasn't answering my land-line.

This struck me as odd. The main reason I hadn't answered my land-line was because it hadn't rung, and I never answer phones which aren't ringing. Actually, it's relatively common for me to fail to answer phones which are, but on this occasion that opportunity hadn't even arisen.

I told my mother that it hadn't rung, that I'd check to make sure it was working, and that she should probably be able to call in about ten minutes. A quick inspection of the phone led me to believe that it was out of battery, but at this point I noticed something rather odd. Every other phone I've used has always plugged into a power socket, or into a charger which in turn plugged into a power socket. There was space for standard batteries, but a screwdriver was required to take the cap off and replace them, and I couldn't be bothered to look for one. I called my mother back on my mobile, and thought no more about it until the next day.

When the next day came, Harry wanted to make a call, and found that he could not. I suggested replacing the batteries, and he went to get a screwdriver. When the cap was removed, it turned out that there had never been any batteries in the phone, and that furthermore, while there was space for them, inserting them would be fruitless. There was no terminals.

I should point out that the phone was working perfectly with no obvious source of power for several weeks prior to this.

Now I am extremely concerned. It seems that the laws of physics are either a lie, or occasionally suspended for cheap electronic equipment. This leads me to worry about my degree - what if my subject of choice is all wrong? What if it's founded on mistakes, which can be proved invalid by a phone that cost less than £10?

I always suspected that if the laws of physics went wrong, it would be something to do with me.

I'm off now, going to go see if I can defy gravity, or build a perpetual motion machine.