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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

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Flight of the Pole Dancer

Shake, Shake Chinook

Crane Overboard!

Physics has given us a great many simple principles that make it easier to understand what’s going on in the world, some better-known than others. To wit: Every action has an equal and opposite reaction; what goes up must come down—both classics, for good reason. And the blingiest of the axioms, E=mc², is particularly useful for understanding why a fistful of plutonium can cause such a big bang. Less famous but far more important on a day-to-day basis if you’re an SUV designer, a high jumper or—as in the present case—a crane operator, is the principle that any object will behave as if all its weight is concentrated at its center of mass.

Finding an object’s center of mass is fairly simple. It’s the point at which half the mass is above the center and half below, half is on the right and half on the left, and half is in front and half in back. If you stand straight up with your arms at your sides, your center of mass is a little below your bellybutton (unless you’re J. Lo). But here’s the important part: If your center of mass is not above your feet, you’re going to fall over. The same principle works for a crane. If the center of mass of the total system—crane plus whatever it’s carrying—moves to one side of the crane’s base, the crane will tip.

As our crane lifts the bus out of the water, trouble is a-brewin’. The water itself is holding up the partially submerged bus. (Remember Archimedes? No? Here: Water pushes up on an object with a force equal to the weight of the water being displaced—this is the reason things feel lighter in water.) As the bus leaves the river, the crane takes on more of its weight until the center of mass shifts so far away from the crane’s arm that suddenly there’s a tip, a splash and the call for a bigger crane. —Michael Moyer

Related:

Flight of the Pole Dancer

Shake, Shake Chinook

Everything has a beat. A rhythm. A frequency at which it likes to shake. You can rock most objects off-beat for as long and hard as you like, and not much will happen (see: the career of John Mayer). But start to push and pull in time with the natural frequency—the “resonant” frequency—of the object in question, and it will quite literally start to fall apart, much like the helicopter in the video below.

I always understood resonant frequencies best by thinking of the old-timey toy the paddleball. This uniquely solitary time-waster—Minesweeper for the Greatest Generation—consists of a bouncy red ball attached by elastic string to a small wooden paddle. Success comes when you hit the ball, the elastic pulls it back to the paddle, and you hit it again. And again and again and again. You quickly notice that there’s only one frequency that works, only one rhythm that prevents you from flailing wildly at the stupid little red ball. This is the paddle’s resonant frequency, and in this case, it’s a good thing.

Not so when dealing with bridges, skyscrapers or helicopters, however. Shake these at their resonant frequency, and the back-and-forth motion spells trouble. Each push adds more and more energy to the object—energy that, if not dissipated, starts to wreak havoc. That’s what happens with our Chinook. The rotating blades begin to shake the airframe at its resonant frequency, and physics takes care of the rest: Because the blades are unable to dissipate the excess energy, the convulsions rend them from the fuselage.

According to PopSci’s aviation expert, Bill Sweetman, helicopters are prone to resonant effects, which is why resonance ground testing (as seen in this video) is a standard part of chopper R&D. If both blades in a twin-rotor helicopter share the same heavy vibration and the engine mounts aren’t rock-solid, the energy generated can actually make the motors start moving around the engine mounts, and the next thing you know, that bird’s goose is cooked.

Sweetman also offered up this anecdotal tidbit: “Little-known fact: Charles Kaman, a U.S. heli designer who was also a bluegrass guitar player, combined his knowledge of acoustics and fiberglass (used in rotor blades) to create the Ovation guitar series.” Cue Patsy Cline’s “I Fall to Pieces”. . .  —Michael Moyer

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The Breakdown: Flight of the Pole Dancer
The Full-Tilt Flying Machine

For a side view of the same test, click here.

On Monday, Fritz Grobe and Stephen Voltz, the two backyard scientists behind the Diet Coke/Mentos experiment, released a sequel to their original phenomenon as the first Google “Sponsored Video”—a new program from our Internet overlords aimed at sharing ad revenue with marquee videographers. The new video (see below), in which the lab-coated duo initiate a domino-effect chain reaction with their famous two-liter Diet Coke fountains, features prominent linkage to coke.com and mentos.com, followed by a short message urging viewers to enter a coke.com-sponsored contest by submitting their own Mentos/Diet Coke–related footage.

The new Google program presents another potential solution to the challenge underlying the explosive popularity of online video: finding the best way to make money from the immense mishmash of user-generated clips. Grobe and Voltz made $35,000 on their first video’s massive viral success via Revver, a YouTube–like site that serves an ad at the end of each video and splits the revenue generated with you 50/50 based on how many times your clip is viewed. The financial details of their current deal with Google, Coke and Mentos are, so far, unavailable.

Unlike Google’s revolutionary AdSense service, which capitalizes on small amounts of targeted-ad revenue collected by millions of smaller sites across the Net, Google video sponsorship will be available only to large-scale content providers with more than 1,000 hours of content or broadcast exposure.

The question remains, though: Is this landmark arrangement a glimpse at the future of online video? Will the second video, with its unabashed commerciality, be as fun as the first one (which even without the obvious branding probably encouraged the sale of lots of Diet Coke and Mentos)? What do you think? Watch it below and let us know in the comments. —John Mahoney

In the pantheon of ubiquitous games (checkers, tic-tac-toe, etc.), Tetris is one-of-a-kind. For starters, there aren't too many members of that pantheon that are videogames, considering they've only been around for a few decades, compared with a few millennia for board games. Even more interesting, though, is the story of Tetris's viral rise from a puzzle-loving Soviet hacker's pet project in the1980s to your Grandma's favorite videogame, all during some fairly heavy Cold War years.

If you're thinking that the intriguing backstory behind one of the Soviet Union's most unlikely cultural exports is right in a BBC documentary filmmaker's wheelhouse, then you would be correct [see it on Google Video here (also embedded below), with props to the fine Kottke.org for the find]. At the core of the game's complicated story is the still-hot issue of intellectual-property rights, in particular the policies of the Soviet era, in which private ownership of an intellectual commodity was a completely alien concept. Seeing Alexey Pajitnov, the game's original creator, recounting in the doc's opening scenes how baffled he was to even think about how a piece of computer software could be sold or protected with a copyright gives an indication of just how crazy the ensuing licensing battle would become, as several international parties rushed to be the first to sell the impossibly addictive puzzle game to the West.

The documentary’s excellent Philip Glass–esque soundtrack and dramatically-lit Russian-official-in-his-office-type scenes make it well worth the 60-minute investment. You could even export it for viewing on your video iPod—that is, if you can stop playing iPodLinux Tetris long enough to watch. —John Mahoney

Having trouble reconciling your love of IKEA furniture with your nostalgia for futuristic, self-reassembling T-1000-like robots? Well, don't fret. Your problem has been solved by a team of engineers and artists at Cornell University who have created the Robotic Chair, a deceptively simple-looking wooden chair that collapses into several pieces and then proceeds to put itself back together.

Described as "the culmination of a 20-year-long investigation into the engagement between the individual and the object," the Robotic Chair is a fine example of computer-assisted robot autonomy. After the chair collapses, the images from a camera mounted above the chair's platform are digitized by a computer with software that converts the location of the chair's pieces from the video into points on a grid. This information is then transmitted wirelessly to the processing unit in the chair's seat, which uses 14 motors and an array of sensors to find its pieces in the correct order and reassemble itself.

This isn't the first time the Cornell folks have dabbled in robotic furniture. Their previous piece, the Table: Childhood, was a table with a brain. The Table, fully mobile thanks to a mechanical set of wheels, could express emotions and even display preferences toward an individual in the room by either following or avoiding a person. Perhaps one day the Table or the Robotic Chair will be honored to join the ranks of the Ig Nobels along with a previous winner, an alarm clock that runs away from you when you try to turn it off.



Whether you appreciate the chair for its artistic value or the engineering skill that went into its creation, or file it away with the rest of the YouTube videos you've been forwarded, just be thankful it was created by people calling themselves the D'Andrea Group and not an organization as ominous or clearly evil as Cyberdyne. —Dan Smith