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What happens when you jump out of a plane and then open a parachute? For Ivan Agudelo "the feeling is kind of like sticking your head out of the window of a car that is traveling at 100 miles per hour." And when the parachute opened Risa Centenni "...felt like a cork flying out of a bottle of champagne!" There must be some pretty strong forces at work to produce such intense feelings. Here's a closer look at the physics of skydiving.

Here is Philippe in free fall without a parachute. At this point the force of gravity is greater than the drag on his body so he is accelerating.

As he accelerates the amount of drag increases, because the faster an object moves through air, the greater the drag.

Eventually drag is equal to the force of gravity. He is no longer accelerating, but rather moving at a constant speed. He has reached terminal velocity, going as fast as he will go. This is roughly 200 kilometers per hour ( 125 miles per hour).

Making contact with the ground at that speed would be rather uncomfortable so Philippe opens his parachute.

With the parachute spread out above him rather than folded up tightly on his back, Philippe plus his parachute present a much larger surface area to the air they are moving through, greatly increasing drag. Since upward force is now greater than downward force, he suddenly begins to slow down. But as he moves slower and slower, drag decreases until...

...gravity and drag are once again equal and Philippe is again dropping at a constant velocity. But now that velocity is only about 22 kph (14 mph)...

...slow enough to make a happy landing.