Built on Facts

Archives for May, 2009

Finally.

Three question E&M I final today, roughly as follows. 1a. As a starting point, calculate the electric potential on the axis of a ring (radius a) of uniform charge. (trivial) 1b. Use the expansion in Legendre polynomials to do an off-axis extrapolation of 1a to find the potential everywhere. (Conceptually not bad, mathematically tedious) 1c.…

T-Rex and Detective Work

Ryan North of the exceptionally brilliant and somewhat esoteric Dinosaur Comics penned a comic a while back about the possibility of being the perfect detective by using physics. Quoth T-Rex in the strip: Someone in the room says something to another person, and then they both leave. Assuming you know exactly how they moved when…

Sorry for the light blogging this week. Finals are this week and next, and so I’m pretty swamped. Today I’m going to pose a straightforward but slightly counterintuitive probability question, of the sort that in modified forms aren’t so uncommon in physics: A densely populated authoritarian state issues the following population control policy: each family…

The Physics of Rapunzel

Our excellent physics blogger Chad Orzel has a post up about the thermodynamics of Goldilocks. Seems it’s a little questionable to have the porridge configured as it was in the old tale. A few wags in the comments complain that in a story with talking bears physics is the least of the concerns, but I…

Sunday Function

“I’d like to open a savings account,” you tell your banker. “Excellent!, the banker says, “our savings accounts have an interest rate of 5% and an annual percentage yield of 5.127%. It’s a great deal and I think you’ll like it.” 5% interest is a great deal on a savings account these days. But what’s…

Well, we’ve explored some groundwork in three previous posts and so it’s time to put it all together. Why exactly do bosons have such weird behavior at very low temperatures, with a large fraction of their number crowding into a single quantum state? Let’s plow on. If you’re not familiar with the mathematics or the…