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## Sticking the Landing

Ordinarily, driving is pretty straightforward: You just point the wheels and go. But piloting an aircraft is trickier, because you not only must deal with complexities like the potential for traffic above and below the plane, but your roadway—the air—moves. Until it’s time to land, of course. Seamlessly transitioning from sky to asphalt is the most difficult thing a pilot regularly has to execute, especially when winds are strong and blowing from side to side (as in the crosswind landing featured in this video). But it’s easy enough to understand what a pilot should do in such circumstances, even if you’re too freaked out to ever in a million years attempt to do it yourself. All you need are vectors.

A vector describes how something moves; picture it as an arrow. The vector’s length describes how fast the thing is moving, and its direction tells you which way it’s going. If you threw a baseball straight up in the air, the vector that described its movement would start out long—the ball’s going fast—and pointed toward the sky. Then the vector would shorten as the ball slowed and, at the top of its arc, would flip downward and grow long again as the ball fell.

If an object is moving in or on a medium that’s also moving—a person on a moving sidewalk, a swimmer in water, a plane in the sky—you figure out how the two will move together by taking the vector for the object and the vector for the medium and joining them together head-to-tail.

In our example, the wind is whipping from left to right, so its vector points that way. For the plane to move straight ahead, its vector must cancel out the left-to-right vector of the wind. That means it has to point a little to the left, or into the wind.

Of course, once the plane hits the ground, it had better be pointing in the direction it’s moving. That’s why the pilot has to straighten the plane out at the last second. If he did it any earlier, the wind would start to pull the plane to the right; if he did it any later, the plane would hit the tarmac sideways and flip over onto its wing. And you thought parallel parking hard. —Michael Moyer

Related:

Flight of the Pole Dancer

Shake, Shake Chinook

Crane Overboard!

Goodbye, Moto

## Goodbye, Moto

Though A-Team reruns would have you believe otherwise, vehicles that crash in real life aren’t immediately and inexorably consumed by giant explosions. Any movie geek knows this. Gasoline doesn’t explode—it burns, just like wood—except in the uncommon environment of an internal combustion engine. Yet our unlucky racer’s motorcycle blows up with such vigor, you’d think Michael Bay placed the explosive charges there himself. So what gives?

The answer lies in the way the bike tumbles across the racetrack. Take a close look at how it flips before conflagration. The first time the bike bounces off the ground, the force seems to knock the cap off the gas tank. As the bike flips again, you can see racing fuel spray out of the top of the tank in great arcs, billowing through the air along with the dirt and gravel kicked up by the skid. This, as they say, is a bad sign.

Gasoline, like every other fuel, needs oxygen to burn. Ordinarily, if you were to set a match to a pool of gasoline, only its surface would burn, because only its surface would be in contact with the oxygen in air. But as it’s injected into your engine, the gasoline is atomized (imagine a tiny gasoline spritzer set on “mist”) in order to thoroughly mix the fuel with air before your spark plug ignites the combination. Since every bit of nearby fuel is now surrounded by oxygen, this flame spreads almost instantaneously through the combustion chamber until everything is alight.

But in the case of the motorcycle explosion, the bike’s acrobatics did the work of atomizing the gasoline. Once a spark ignited the little droplets, the whole thing went up in a bang. So a word to the wise: If you’re going to have a catastrophic accident in a motorcycle race, try to keep your gas cap on. —Michael Moyer

Related:

Flight of the Pole Dancer

Shake, Shake Chinook

Crane Overboard!

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### June 2013: American Energy Independence

Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.

Online Content Director: Suzanne LaBarre | Email
Senior Editor: Paul Adams | Email
Associate Editor: Dan Nosowitz | Email
Assistant Editor: Colin Lecher | Email
Assistant Editor: Rose Pastore | Email

Contributing Writers:

Kelsey D. Atherton | Email
Francie Diep | Email
Shaunacy Ferro | Email

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