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The Physics of Skydiving

4 minutes

(Describer) Title: Science Out Loud. Packing parachutes, two men and one woman zip up skydiving suits. They pull the packs onto their backs, and tighten their straps.

(Describer) One sets an altimeter worn like a watch, and another pulls on gloves.

(Describer) They all pull on helmets with clear face shields. As a skydiver drifts down with an open parachute, the woman and men walk in slow motion and get titles over them: Swati, Banks, Andrew. They join several others boarding a small plane, which taxis and takes off.

(Describer) Later, they’re above some small puffy clouds.

Yeah!

(Describer) With a side door open, Swati and Banks drop out and hold each other’s hands.

(Swati) The MIT Skydiving Club just jumped out of an airplane. It might seem like a wild adrenaline rush, but there's more to skydiving than jumping from a plane and pulling a ripcord. Skydivers can control their falls. They can sit, track, flip, fly head-down, make crazy hybrids, and even fly over to each other to dock.

(Describer) On the ground...

(Andrew) When you're falling a few feet, you can't do much on the way down. How is falling thousands of feet through the sky different? Things accelerate towards the ground because of gravity.

(Describer) On the tarmac, Andrew:

But when skydivers fall for thousands of feet, another force becomes important. Drag!

(Describer) Swati skydives.

(Swati) Gravity pulls skydivers toward the Earth. But as we fall, tiny air molecules bump into us.

(Describer) ...shown as animated bubbles.

Each tiny bump causes a bit of force against our bodies. The hit from one air molecule may not seem like much, but all those tiny forces make a big force called drag, which pushes up against gravity. You feel drag when you stick your hand out of a moving car.

(Banks) When jumpers first leave the plane, there's little drag, so they accelerate toward Earth.

(Describer) Banks falls.

As the skydivers fall and speed up, they feel the force of more and more air molecules. By positioning our bodies, we can gain control by pushing against the air.

(Describer) On the tarmac...

If Banks and I want to jump together, can we fall at the same speed? Swati has less surface area so you'd think she'd fall faster. But because she's lighter than me, she falls slower.

(Swati) By reducing the surface area exposed to air molecules, I can reduce drag and keep up with Banks.

(Describer) They face each other in the air, and others join them.

Drag is used for more than speeding up or slowing down. Moving your arms to the side and legs out generates extra airflow at your feet, which pushes your body in the direction it's facing.

(Describer) It looks like diving in water.

This is called tracking. To use drag, air must push you hard enough, if you're going fast enough.

(Describer) At a pool...

That's why you can't track when you jump off of a high dive.

(Describer) She turns to a man jumping in feet-first.

(Andrew) Skydivers can also turn in place to create formations with each other. Positions like sitting, standing, and head-down change the surface area, and because fewer air molecules hit their bodies in these positions, skydivers can reach speeds up to 200 miles an hour. Skydivers would prefer, though, to not hit the ground at 200 miles an hour.

(Swati) Because they can't change gravity's pull, they need the maximum possible drag, so they open a parachute.

(Describer) One opens. On the ground...

The parachute's large surface area helps us to slow down so we can land safely.

(Describer) One lands on a cross on the ground.

(Swati) Skydiving appears to defy the laws of physics. But in the end, it's just playing with the wind.

(Describer) Title: Made with love at MIT. Accessibility provided by the US Department of Education.

Accessibility provided by the U.S. Department of Education.

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It seems like something strange is happening with the laws of physics when falling thousands of feet from the sky. Turns out, everything relies on the simple force of drag. Part of the "Science Out Loud" series.

Media Details

Runtime: 4 minutes

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