Sunday, January 9, 2011

The physics of triathlons

Naomi did get a few pix in before finding out that cameras were forbidden
When teaching physics to high schoolers, you have to put up with a bit of whining. When are we every going to use this stuff? Why do we need to know that? I had taught diluted physics to high math ability 10th graders back in the day (and at night, low performing adult math students..quite a contrast). I tried to give practical examples as much as possible. I had them determine their reaction times using a meter stick and the formula
 d=(1/2)gt2 . We discussed relativity. You are walking to the back of the train at 2mi/hour. The train is travelling due east at 60 mi/hour. What is your actual speed? Relative to the train. Relative to the earth. Relative to a fixed point outside of earth. Relative to the ....

Back when I took physics in high school, I remember calculating the height of the WXYZ broadcasting tower that was about 3/4 of a mile away with crude surveying tools we constructed so we could get the angles from 2 different points at a known distance and a table of trig functions (we did not have calculators preloaded with these certainly would have made our lives easier).

We dealt with vectors. You are paddling across a 1 mile wide river at 2 miles an hour. The current is a steady 3 mi/hour. How long does this trip take? How far did you paddle? Use d=vt and the Pythagorean theorem.

When doing triathlons, I thought about these vectors especially in the swim. Fortunately small inland lakes generally have negligible currents and usually I just had to deal with being tangled in seaweed, fuel slicks from motorboats, waves,  getting my goggles kicked off by my fellow triathletes, trying to swim in a straight line with spotty points of reference, being cold, not panicking, getting tired...One year I did the Chicago triathlon which at that time consisted of a 1500 m swim in Lake Michigan, a 25 mi bike ride, and a 10K run. To enter, you had to certify that you were capable of swimming a mile (which I had since I swam a different race by the same organizers). They mentioned though that if there was an east wind (we swam east more than any other direction), we better be capable of swimming 2 miles. Of course there was a strong east wind when we awoke that morning, which was good news for the bike leg as we were travelling north and south on Lakeshore Drive with little travel east.. A 20 mph wind doesn't turn into a 20 mph current to fight against but even if it translated to a 2 mph current I was hosed if all I was capable of was swimming 2 miles an hour. I'd be swimming in place. Cross currents would add to your time too particularly if you were slow. See Pythagorean theorem.

They said the water was 66 degrees, which maybe it was near the shore where they measured but there seemed to be pockets of ice water that made me gasp. I considered bailing unless I could get my breathing slowed down..calm down! calm down! Eventually I was able to get into a rhythm. Unlike many of the lakes I did races in, Lake Michigan is actually clear and I could see the bottom (way, way down there). I found myself swimming on top of some old sea wall that seemed to be parallel to the shore. Looking up constantly to orient cuts into one time. I did look up and found that by fellow racers had cut into the shore to finish. Ugh!

Biking against a strong wind actually is helpful to the weaker riders. Wind resistance is proportional to  the square of the speed meaning doubling the speed would quadruple the wind resistance. Attempts to reduce this resistance from tucking behind another rider (drafting) was forbidden. Riding a bike that minimized resistance was OK.
Surprisingly (to me) bike spokes are a considerable source of resistance so solid wheels  are sometimes used (tough with cross winds though). Tucking your body down as much as possible maximizes speed but hurts the back. Making sure you aren't wearing baggy clothes helps too. Toe clips maximizes the energy transmitted to the crank so none is wasted trying to keep your feet on the peddles and on the upswing part of the cycle. But you need to remember your feet are locked in if you have to suddenly stop (I forgot this once..ow!).

Wind resistance is less of a factor in running due to the lack of speed involved. It actually helps in cooling on hot days. Still on very windy days in races, I sometimes tucked behind a big man (and would feel somewhat insulted finding people behind me using me as a human shield).

When snorkeling, there were often currents to deal with. I would swim against the current to view a particular reef so that I would not be dashed against it. Also it would keep me warm as snorkeling is not as heat generating as swimming. But the sea introduces more challenges: sea creatures which is why I was snorkeling in the first place. Jelly fish though are no fun.

When visiting my in-laws off of Coney Island, sometimes I would train swimming beyond the breakers parallel to the coast. Once I became sea sick rising up and down with the waves. You adjust your breathing to the waves. I tried to avoid swimming near the breakwaters so I would not get dashed into them. When doing aerobic exercise, endorphins are released. I could overlook minor pains. Once though while swimming in the Atlantic I felt intense stinging underneath my suit. I stopped, took off my foggy goggles and found these tiny translucent baby crablike things pinching me. I have since read that there are blooms of sea lice, infant jellyfish that are capable of stinging but these things seemed to have pinchers and eyes. Suffice it to say, I cut my swim short that day.

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