Built on Facts

A while back the county government in my home town was considering a request from a phone company to construct a new cell tower to bring cellular service to a rural area. The government balked, largely for aesthetic reasons, though they couched their opinion in safety terms. They said they were concerned about [...]

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Like the Batman problem a few posts down, there’s another classic failure which has reached internet fame and glory by virtue of its spectacular flameout.

Wonderfully eccentric, but the sad part is that the problem is literally one line away from a correct solution. The block starts off with a gravitational potential energy mgh. [...]

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Quantum mechanics is difficult. “Yeah, yeah,” you say, “tell me something new”. But it’s not only a bit tricky to learn. Mathematically there’s simply not a way to get exact solutions to all of the problems we face. They just don’t exist in a nice short closed form. But we’d [...]

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There’s a test problem famous by virtue of the fact that one student failed to answer it, but did so in a hilarious way. You’ve probably seen it, and here it is:

Let me quote the problem in case it’s hard to read.
A proton approaches a long line of positive charge so that with its [...]

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My intro physics text in my undergraduate education was by Halliday, Resnick, and Walker. I personally thought it was a quite good text, but what particularly stood out was its obsession with penguins. Probably a dozen or more problems involved penguins in very improbable situations. It was pretty funny. But there’s [...]

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In honor of the NBA playoffs, how about some quantum mechanics? Ok, maybe it’s a stretch! But let’s say we have a particle bouncing on a hard surface. We can model this by defining a floor at x = 0. For x > 0, the potential V(x) = mgx. For [...]

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We live in a nice, classical world. We can tell where we are and how fast we’re going. We can spin things around at whatever speeds we feel like, and if we throw something through the air we can predict where it’s going to go.
Quantum mechanically, however, things are a lot fuzzier. [...]

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The divergence theorem? Gauss’ law? If you’ve had college physics, at least the second is familiar to you. Now those two things are really fascinating, and I’m going to put a math-lite layman’s explanation in a future post. But hey, it’s spring semester finals time and that means all you people [...]

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Many of my students had their final exams today. In the weeks leading up to the exam, we reviewed by doing homework problems and working final exams from previous years. Here’s one of the questions:
Protons of velocity 5×106 m/s are moving perpendicular to electric and magnetic fields which are crossed at right angles [...]

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