Built on Facts

Archives for February, 2009

Some ‘splainin to do!

There was, if I am not mistaken, an episode of I Love Lucy wherein Lucy manages to get her head stuck in a metal teakettle. Ethel jokingly (I hope!) suggests that she put her head in the oven to heat up the metal so it will expand and she can fit her head out. A…

The physics of… Pink Floyd?

In full early-90s nostalgia mode, you skate down the street in your roller blades. Your thrill at the excitement of the open road distracts you, and one foot goes off the pavement into the soggy soil beside the road. That foot immediately slows down due to the drag and as a result of the difference…

Earthquake!

Every section of Physics 218 I’ve taught this semester has asked me about this question. Really it’s less of a physics question than it is a math question, but either way it gives people fits. It’s not all that surprising. While it seems like it should be simple, to most beginning students it’s not at…

Physics Poetry

A little off the beaten path today, I’d like to present two poems by two physicists who were both on my Ten Greatest list. They’re very different, one contemplative and loose in form, the other playful but more rigorous. It’s an interesting comparison. Untitled Richard Feynman There are the rushing waves… mountains of molecules, each…

Challenge Problem!

This one’s from Young and Freedman, and I pick it out because it’s both from the chapter I’m teaching and it’s a great conceptual problem as well. (I’ve modified it slightly.) A shotgun fires a large number of pellets upward, with some pellets traveling vertically and some as much a 1 degree from the vertical.…

Sunday Function

Continuing my series of basic concepts with middle school math will be tricky when we’re doing a Sunday Function. But let’s give it a shot, and see if we can keep it to that beginning level. This function is pretty simple. You add reciprocals until you get reach whatever number n you’ve picked, then you…

A contrarian view of the stimulus.

And when he had opened the third seal, I heard the third beast say, Come and see. And I beheld, and lo a black horse; and he that sat on him had a pair of balances in his hand. – Revelation 6:5 Well if everyone’s going to talk about the financial crisis like it’s the…

Indistinguishability

Continuing our “basic concepts with no math” series, here’s one of the most important for quantum mechanics and statistical mechanics. To start, imagine a billiards table. It has an assortment of billiard balls, each numbered and colored differently. You can imagine randomly knocking them around the table, sort of in analogy to gas molecules bouncing…

The Central Limit Theorem made easy

Ok, so yesterday wasn’t quite as basic as I planned on shooting for in this week or two of working on non-mathematical concepts. But the idea was too cool to resist. This isn’t exactly a mathematically elementary subject either, but the concept can be grasped without needing to see the actual functions involved. This is…

The Physics of the Death Star

Standing on the edge of Niagra Falls you can watch the water pour over. Falling down the gravity of the earth, it exchanges its potential energy for kinetic energy by picking up speed. Some of that energy is extracted by turbines and lights the homes and businesses of Yankees and Canucks alike. Some of that…