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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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The Physics Behind The Perfect Dive

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kingon posted on 2016/08/18
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