Sunday, June 21, 2009

The relationship between math and free beer

Last night, J. and I came home via the meandering Rte 25, rather than the interstate. As we approached Old Clay's Ferry Bridge, a narrow bridge eclipsed by the newer bridge towering far overhead, we saw a group of foolhardy young men wearing lifejackets and swimming trunks. Apparently, Riptide Bar and Restaurant had offered free beer to anyone stupid enough to jump off the bridge, and these guys were stupid enough (and tipsy enough) to volunteer.

We pulled over to watch. One by one, they stepped off the bridge and plunged inelegantly into the brown water below. I think one guy was unfortunate enough to smack full-body onto the surface of the river (I'm sure this has happened to all of us at least once when we were kids and learned through painful experience that water actually has surface tension).

Never one to pass up an educational moment, Jon calculated the approximate distance between the bridge and the river, using the formula:

p = p0 + v0t + ½ at2



He knew several of the variables. Every second a body accelerates with gravity, it increases its speed by 32 feet per second, ignoring air resistance and our trivial distance above sea level. This number is a. We also assumed that each guy's initial velocity relative to our reference point (the bridge, p0) was 0--in other words, they were just stepping off the bridge, not jumping up or down. This number is v0. We knew that it took each guy approximately 1.5 seconds to embrace the water, so we used that for t.*

p = 0ft + 0fts-1*1.5s + ½ 32fts-2*1.5s2


Which gives us the answer 36, so we can make an educated guess that the bridge is between 30 and 40 feet above the water.

Now you've learned something for the day.

*J. helped me write this paragraph

1 comment:

dwain said...

Freaking awesome.