Built on Facts

Archives for August, 2008

Sprinting and Sound

Congratulations to all the Olympic athletes who have competed thus far, especially Michael Phelps, Nastia Liukin, and Shawn Johnson. Gymnastic events are all great to watch, and I don’t think you could find a more colorful analyst than Bela Karolyi. The balance beam is probably the most classic and thrilling gymnastic event – the Summer…

You can break the laws of your local jurisdiction. It might not be a good idea, but if you want to drive 60 in a 45, you can. You’ll pay a hefty fine if you get caught, but you’ll still have been able to do it. There’s no penalties for breaking the laws of physics…

What Impulse Is.

This is Zhang Juanjuan, immediately after applying an impulse to an arrow. Impulse is something which gets less airtime than work in freshman physics, but it’s nonetheless very important. It’s sort of momentum’s version of work. You’ll remember from Monday that there are two main things to keep in mind about work. 1. Work is…

Zap

This is more technology than strictly physical science, but I’m professionally interested in laser physics. My own area is mainly attosecond pulses at modest average power, still, the applications of broader laser technology are always instructive. Boeing has been working on laser weapons technology for a while now. I’ve written about it before, mainly from…

What Work Is.

This is Liao Hui, not doing any work. He did work to get the weight over his head, but despite the tremendous force he’s applying to this 348 kilogram [Update: Thanks to commenter Ducklike for correcting this to 158 kg] weight he’s not doing any work in this picture. The weight is stationary. Work in…

Sunday Function

You all know what the natural log function looks like. Take the number 1, divide it by the natural log, and then find the antiderivative of that function. You’ll get the logarithmic integral function. It looks like this: Sometimes the lower limit of the integral is changed to 2 instead of 0, in order to…

Carrying Guns on Campus

Greg Laden responds to the recent change in policy allowing teachers with concealed carry permits to carry in one particular public high school in north Texas should they so choose. If only the teachers had guns…. (Texans = Morons). Here’s CNN’s original story. The school is a 30-minute drive from the nearest police station, and…

Saturday Goofing Off

A quick Olympic question: How would a native of China pronounce the j in Beijing? All the commentators pronounce it like the J in the French je suis, but I’ve heard that in China the pronunciation would be closer to the J in jingle. I have no idea if this is true, and I’m not…

Temperature of a Microwave

What’s the temperature inside a microwave oven? I’ve seen some thermodynamics textbooks start off with a preliminary definition of temperature that amounts to “The temperature is what a thermometer says it is”, since temperature is really a concept that fundamentally is derived from energy and entropy. So the books like to discuss those at length…

Conservation Laws in Collisions

I think it’s time for a good old practice problem. This is a pretty basic one, which you might encounter as a freshman physics major. The general concept of dealing with inelastic collisions is one that you never escape, and from special relativity to quantum mechanics this type of thing keeps appearing in new contexts.…