Going Up T e balloon stops rising aſt er two hours. Now, it’s 39 km (24 miles) above the ground. T e capsule door rolls open, and he steps onto a ledge. Above him, he sees the blackness

of space. Below, he sees the curve of Earth’s surface. T ere is no time to waste. He only has about 10 more minutes of oxygen. T at’s about how long his fall will take. “I’m coming home,” he says, as he steps forward.

A Change of Energy He dives. He picks up speed. Earth’s gravity is pulling him down. It’s also changing how his body uses energy. Here’s how. Before he jumped, he had a lot of

potential energy. He wasn’t moving at all. All his energy was stored. Yet he had the potential to move fast. Aſt er he jumps, gravity tugs on

him. Now, he’s using kinetic energy. T at’s the energy of a moving object. He falls faster and faster.

air pressure: the force of air pressing on a surface

gravity: a force that pulls objects toward each other

Spinning About 30 seconds into the fall, the skydiver starts spinning. It looks like he’s doing cartwheels. T at’s not good. If he spins too fast, he could faint. So he fights the spin. He sticks out

one arm. He spins faster. He pulls it back in. He sticks out the other one. He slowly stops spinning. He falls 1,385 km (844 miles) per

hour. It’s a speed record! No one has ever gone that fast in a free fall.

Landing Now, he’s closer to Earth. T e air is thicker. He’s still falling, but he starts to slow down. He opens his parachute. T e chute

catches the air. He floats the rest of the way to the ground and lands safely. Nine minutes and 18 seconds aſt er he jumped, his free fall is over. He feels great. He pumps his fist in

the air. All the planning and fear were worth it. “Adventure,” he says, “is how we learn.”

kinetic energy: the energy of a moving object potential energy: stored energy stratosphere: a layer of Earth’s atmosphere

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