The Course
The bike course started in Cleary Lake Park. We all saddled up and headed out on the 13.5 mile journey. This was a pretty easy trek for the other 3, but it was more of a challenge to me because (a) I just don't have the cycling fitness that they do, and (b) I've got a mountain bike whereas they all had nice road bikes.
The course itself traveled through rural farmland, and had some gentle rolling hills to start. And, by gentle rolling hills, I mean Mount Everest. Not really, but they seemed that way to pokey old me. The difficulty I ran into was that I needed to conserve as much momentum as possible (engineers: I know momentum is always conserved—just go with it). I wanted to keep my speed up on the downhills so I didn't die on the next uphill. However, the others could take it nice and casual on the downhills. Therefore, I looked like the jerk who passes people just to get passed a few seconds later.
I didn't die, but there were some treacherous rumble strips to look out for. They're actually quite jarring on the bike, but I guess I have an advantage with the suspension on my trusty old mountain bike. Sorry roadies…
We got back, and Katie did pretty well. Her shoulder was sore, but it's feeling better now. The three of us that weren't
We were discussing the ethics of ignoring the beach rules
I think Katie's goal in life is to take awkward pictures of me
You can see the blue "beach curtain" in this photo
We ended up doing very little swimming. The weeds and the beach curtain made it pretty much impossible for us to get beyond the swim area, so we stayed within the small swim area. They'll be opening the curtain for the triathlon, but it would have been nice to swim out into the lake to work on sighting. I also realized that I looked kinda dorky wearing my wetsuit in the swim area. The goal was to go beyond the swim area, but by the time we realized we couldn't, I already had it most of the way on. So, I looked a little silly, but I was warm and buoyant. (You don't hear people calling themselves "warm and buoyant" everyday, do you?)
After about 100 meters of swimming, we called it a day. Katie then got distracted by a puppy. It was morning, evening, 4 days later… Katie left the puppy alone. We're hoping to come back and ride the course one more time, and maybe swim again so Katie can get used to the water. We'll probably need to enter at the boat ramp, though, to avoid the curtain.
Katie is still on the mend, but she's pretty sure she'll be doing the Croixathlon this weekend. Look for more coverage on that later.
2 comments:
Alrighty, let's think for a second about your momentum analysis on the biking ...
You do indeed want to MAINTAIN your momentum (a more concise word than conserve in this case), so let's do a momentum balance on a biking Matt. First of all, there is a momentum source that comes from chemical energy stored in Matt's body which is converted into momentum by pedaling the bike. Next, consider momentum sinks (or momentum dissipation mechanisms). The non-elastic deformation effects in the tires combined with friction dissipates a small amount of momentum, but this can be considered negligible. The dominant mode of momentum dissipation comes from wind resistance.
Thus, we have a simple system with essentially one momentum input (Matt's legs) and one momentum output (wind resistance). The momentum of Matt will be determined by the difference between these two mechanisms.
Being how this is an endurance sport, the general goal is to cover a certain distance in a certain time with the least amount of pedaling (aka we want to minimize the momentum input). Thus, in order to optimize biking efficiency, we need to minimize the momentum dissipation due to wind resistance (because it is the only output to the momentum balance). We know that wind resistance generally goes as the square of the speed, so increasing speed is going to decrease efficiency.
Ergo, pedaling fast down hills increases cumulative momentum dissipation and requires more energy input from Matt's legs. To be the most efficient he should coast downhills and pedal hard up hills when the wind is not holding him back. QED
Very good David. However, you made one incorrect assumption. Yes, the wind resistance is a function of the speed squared. What you forgot was that I'm slow, and the square of zero mph is still zero. Thus, wind resistance is negligible for a slowpoke like me.
QED
Post a Comment