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Fermi Problem Friday

How many times do your bicycle wheels spin around on your way to school?

Bonus question: Is this the same number of times your feet pedal around?

This might be difficult to answer if walk to school or take a train. In either case just cycle your feet around and pretend you are riding a bike. If people look at you funny, just tell them it's a physics project.

This excuse always works in any situation. For instance if you trip on the sidewalk and onlookers start laughing, just tell them you were testing Einstein's Theory of General Relativity. Suddenly they will be impressed.


  1. My feet pedal around 1/3 the number of times as the wheel (fixed gear bike, 48 tooth front to 16 tooth rear), and with a roughly 27" diameter tire that's 7.06ft/turn, or 747.5 rotations per mile. I go ~10 miles, so ~7500 turns of the tire in that time, and ~2500 swings for each leg.

    The rear inevitable spins slightly less than the front due to cornering too, which would be a very hard thing to calculate.


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