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  • I see a 10 meter drop into a pool and think I’m going to die.

  • Divers see a 10 meter drop and think, “How can I bend physics to make this awesome?”

  • Greetings mathletes, HOST here for DNews.

  • The summer games are upon us!

  • The best the world has to offer have gathered to play just about every sport under the sun.

  • And while each sport has its own unique appeal, from a physics perspective there may be none

  • more interesting than diving.

  • Divers are spinning, flipping, twisting water ninjas that have bent the laws of physics

  • to their whim with nary a splash.

  • How do they do it?

  • Let’s take it from the top.

  • Be it from a springboard 3 meters up or a solid platform a dizzying 10 meters up, the

  • initial leap is all-important.

  • First off when the diver jumps they have to make sure theyre not going to end up where

  • they started; on a concrete platform 3 stories in the air and decidedly dry.

  • Failing to clear the platform or board is a big no-no, so the diver has to give themselves

  • some forward velocity, meaning they will travel in an arc until they hit the water.

  • The diver also wants to get as high as possible, because more time in the air means more tricks

  • they can pull off.

  • The final dimension determined at takeoff is the diver’s rotation.

  • If theyre going to spin and flip, they need to start that from the jump.

  • But they can increase the speed theyre spinning as they fall by drawing their body

  • into a compact ball.

  • This tuck position reduces what’s called theirmoment of inertia,” the body's

  • tendency to resist angular acceleration.

  • When the moment of inertia goes down, their rotational speed goes up to conserve their

  • rotational momentum, more commonly known as angular momentum.

  • The result is divers can squeeze four and a half flips into a second and a half of fall

  • time.

  • The other commonly used position for increasing spin speed is called the pike, but unlike

  • the tuck the legs are kept straight, meaning the diver has less control over rotational

  • speed, and the dives have a higher difficulty.

  • Of course all the flips and spins in Rio won’t get a diver a good score if they finish with

  • a belly flop.

  • Diver’s have to spot the water to know when theyll splash down, no easy feat when theyre

  • twisting and rotating and traveling at 51 kilometers per hour after falling 10 meters.

  • When it’s time to get wet, the diver’s goal is to enter the water with as little

  • splash as possible.

  • If they do it right, theyll part the water with a sound like ripping paper, known as

  • a rip entry.

  • To achieve this the diver has to punch a hole in the water and enter it as straight as possible.

  • Remember though that because angular momentum is conserved, theyre still spinning when

  • they straighten out, just more slowly.

  • Their body still rotates underwater, but masterful divers will hit the surface in such a way

  • that they look like theyre going straight in.

  • If they can pull off the rip entry after flipping out more than a teenager’s mom, they stand

  • a chance of making a splash at the summer games.

  • Concepts from physics are hiding everywhere in sports.

  • To learn how theyre crucial to throwing a wicked curveball, check out Julian’s video

  • here.

  • What’s your favorite physics-al activity?

I see a 10 meter drop into a pool and think I’m going to die.

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B2 US diver rotational angular water momentum speed

The Physics Behind The Perfect Dive

  • 68 1
    kingon posted on 2016/08/18
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