[Author's note: 'Not sure how interesting this will be to you folks, but since I'm out of town this week, it's all I could come up with for "Central Oregon tech" - couple of geeky sports links, and a fun physics thought exercise. Feel free to bitch in the comments if you think this is a waste of time. 
]
I’m a big fan of XKCD.com, an online comic strip that is unabashedly about and for geeks. The author, Randall Munroe, in a recent blog post, talks about sledding on an icy hill and the (quite natural I think) thought exercises about conversion of potential energy to kinetic energy that it evokes. This seemed particularly apropos given how icy the sledding hill at Wanoga Snow Park was last week. (‘Not sure about what it’s like this week since I’m in Manhattan right now, where it is cold, sleety, and depressingly flat 
). I’ve often found myself doing similar calculations while recreating in the great outdoors and this inspired me to work through a problem that’s bugged me for a while:
How many calories do you burn when you ride from Bend up to Mt. Bachelor?
If we dust off the ol’ high school physics textbook (meaning Google’s search field) we’ll find this equation for power:
(P)ower = (H)eight * (M)ass * (G)ravity / (T)ime
Height we can get from the [awesome!] bikely.com website, where we see on the elevation profile for Bend to Bachelor (click Show -> Elevation Profile) that the “meaty” section of the ride is a 16km stretch that rises 850 meters. For the rest we’ll assume an average rider “Fred” who, together with his bike, weighs 90kg (198 lbs) and who can ride this stretch of road in one hour. Thus, we have:
- H = 850 m
- M = 90kg
- G = 9.81 m/(sec*sec)
- T = 3600 sec
Crunch the numbers and we see that Fred’s average power output is 208 watts. To find the total energy used to climb the hill, we multiply by 860 calories (little ‘c’) per watt per hour and get 178,000 calories, or 178 Calories (big ‘C’ – the units used on food labels).
… Wait, what? Only 178 Calories to bicycle up Mt. Bachelor? Preposterous!
‘Turns out we’re not quite done yet. Our muscles are only able to convert 15% of the food-energy we consume into mechanical energy. To generate that 178 Calories of energy, Fred has to consume 1186 Calories.
So, the next time you find yourself grinding your way up to Mt. Bachelor, you can rest easy in the knowledge that you’re burning off that McDonald’s Deluxe Breakfast you just ate. Ugh.
Linkage:
- Bicycle performance stats (e.g. the average rider produces 200 watts at peak output, or about 1/4 horsepower).
- Bicycle routes around Bend
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