Wednesday, March 16, 2011

Measuring "pi"

Rhett Allain had an interesting post for "Pi Day" concerning the use of a simple harmonic oscillator consisting of a mass on a spring to measure pi. Clever!

However, he neglected the effect of the spring mass. The correct formula for this problem requires the addition of 1/3 of the mass of the spring to the mass hanging on the spring, which appears inside the square root used to calculate the value that goes on the x axis of his fit. Although it is really hard to tell what his fit looked like or what the mass of the spring might be, including this necessary effect should increase the slope and make his result worse.

Nice idea, however. I'll have to give this a try when we have the lab setup.

That said, I have special praise for his OUTSTANDING blog about how to build you own energy balance thing. I did the human demo in one class before spring break, and might have saved some students some money if the showmen are out on the beaches this week. The plastic version looks like it might make a good demo all on its own ... even without the cute crown with its cell phone re-receiver energy recycling thingy.

1 comment:

Sherman Dorn said...

That reminds me I need to (okay, want to) find time to read Mark Levi's The Mathematical Mechanic. The gedankenexperiment approach to the Pythagorean Theorem was charming, but I haven't gotten any further.