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• The electric light, the telephone, the microchip.

• All great inventions.

• But for me, the most important of all

• was the wheel, mainly because it led to things like this.

• Downhill cycling.

• Why use two wheels when one makes you look twice as cool?

• But before you even think about pulling off a downhill wheelie,

• be aware that even on two wheels,

• it could still be perilous.

• What makes downhill cycling is such a terrifying pursuit

• is that the bike isn't only powered by the cyclist's legs,

• but also by our old friend gravity.

• When a cyclist goes up a hill, he gradually gains

• gravitational potential energy.

• When he descends, this gravitational potential energy

• can be converted over a very short period of time

• into a terrifying amount of kinetic energy.

• If the rider falls, that kinetic energy might be converted

• into heat via friction, or if they stop suddenly,

• dissipated via deformation.

• So energy is never destroyed.

• It's merely transferred into something else

• like kinetic energy, heat, or even the sound

• of an impact, which is often accompanied

• by the sound of screaming.

• To investigate, we sent out some of our more

• reckless researchers.

• This guy has made a deal with gravity

• and built up a lot of kinetic energy.

• So much so that he's able to pass cars.

• Except that one.

• The cyclist is unable to transfer

• enough kinetic energy into heat the friction at its brakes.

• When he hits the car, his remaining kinetic energy

• is transferred into sound, heat, and dissipated a deformation,

• also known as bouncing off.

• Don't worry.

• He was OK.

• All right.

• Let's try a gentler pace.

• This is more like it.

• A chance to take in the scenery.

• And his friend's bottom.

• He appears to make no attempt to reduce his kinetic energy.

• And his linear momentum becomes angular momentum

• as he rotates around the axle of the front wheel.

• And maybe not the last.

• Perhaps it's safer to go downhill on three

• wheels with these drift trikes.

• Or maybe not.

• It's just as well our drift trike gang are

• heading home on four wheels.

• Maybe safer just to walk.

The electric light, the telephone, the microchip.

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B2 kinetic energy kinetic energy downhill cyclist cycling

# The Perils of Downhill Cycling | Science of Stupid: Ridiculous Fails

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林宜悉 posted on 2020/12/04
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