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Blogging with the Walshster

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The physics behind a bicycle's drivetrain

A bicycle's drivetrain includes the pedals, cranks, bottom bracket, gear rings, chain, sprockets, freewheel, and derailleur. With all of those parts working in harmony, it takes the power provided by a human pedalling at 90rpm and uses it to turn a 27.75" diameter wheel at 20mph, all with an efficiency upwards of 95%. The drivetrain is, essentially, a system of levers and adjustable pulleys, working together to convert torques and forces. A typical crank is 175mm, measured from the center of
walsh416

walsh416

0

Turning a bike!

Golly gee biking (cycling) is hard. Perhaps the hardest part of all is mastering high speed cornering. You see it all the time in the Tour de France; pros carving graceful arcs as they fly down mountainsides at 100kph. How do they do it? By maintaining an incredible awareness of where their center of mass is relative to their bike at all times, and adjusting it so that they can achieve the right angle of cornering. By far the most common mistake any new cyclist will make is to turn their
walsh416

walsh416

0

Catapult Day!

So we launched catapults on Friday, that was pretty intense. In theory, ours was utterly perfect. We optimized it mathematically, and built it with the strongest $1.99 2x4s in all the land. What we didn't account for was wind. Not wind's effect on our projectile, but on the catapult itself. When cocked, our catapult had 135 pounds roughly four feet in the air (about 700 joules of potential energy, for those keeping score). During one launch our catapult, well, fell on me. If it fell two
walsh416

walsh416

2

Sandra Bullock is an Idiot

So I went to see Gravity this weekend. Overall, it was pretty good! Unfortunately, Sandra Bullock was truly brain dead throughout much of the film. In one memorable scene, she's trapped inside the International Space Station, alone, and fighting a massive fire. Panicking, she grabs a fire extinguisher off the wall and aims it. Now, before we get to what happened, it is important to understand a few things. The character she is portraying is an MD Ph.D, with years upon years of education.
walsh416

walsh416

2

Relax, I'm Here.

Ever since my birth in a log cabin in Montana, I've made a hobby of moonlighting in all of the occupations listed here, proceeding through them alphabetically. Personally, I've found I have a real interest in Taxi and Exotic dancing, grioting, and mechanical/aerospace engineering. I cannot wait to learn about all of these within AP Physics C. My strengths include algebraic manipulation of numbers and a truly superior superior vena cava. I think I can certainly stand to improve my sink-throwing s
walsh416

walsh416

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