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## Slip-Slidin' Away

Good thing the cars in this video are all moving slowly. Add a little more speed, and the scene would be a driver’s worst nightmare. Imagine a car pileup in front of you on a snowy day, your own skidding wheels and, seconds later, the inevitable crash…

Consider—the reason people can control their cars is that it’s very hard to slide a tire across pavement. Technically speaking, this is because tires are built to have a high coefficient of friction when pressed on a paved road. The coefficient of friction is essentially a ratio of the force it takes to slide two surfaces across each other to the force they’re being pressed together with. A high coefficient of friction means the two surfaces don’t like to slide; a low coefficient of friction means it’s easy. For example, let’s say you’re speeding down the highway and you see a police officer, so you step on your brakes. The amount of force it would take for your car to skid is the weight of your car (the force pressing the car to the road) multiplied by the coefficient of friction. When the pavement is dry, the coefficient of friction is high, so you can apply a lot of braking force without skidding.

On the fateful snowy day in our video, things worked a little differently. When these people pressed the brakes, the heat generated by the tire-on-ice friction created a thin film of water over the frozen surface. The coefficient of friction for tires on ice with a thin film of water between them is pretty much zip, resulting in—you guessed it—auto Ice Capades. It took almost no braking force for the cars to skid and, once skidding, they continued in a uniform motion, on a decline, until they found something that could apply enough force to stop them. The most convenient thing, as it all too often is, was another car.

There’s not a whole lot you can do in a situation like this besides try to steer out of the line of other cars and gently brake in the hopes that your antilock system helps the wheels grip again. What didn’t seem to work was when one guy jumped out of his car, grabbed the door, and tried to stop it himself. Maybe he can bench-press a few, but it’s doubtful he could have competed against the villainous combination of ice, rubber and a low coefficient of friction. —Katherine Ryder

Related:

## Minigames Get Big on the Wii

 Even grandma loves the Wii. Photo by AZAdam

From the beginning, Nintendo's mission with the Wii console was simple—to use an innovative motion-sensing controller to open up the world of console videogames to an audience not exclusively composed of teenage boys. As a direct result of this mission, one particular genre seems to be getting a lot of attention in the console's first few months, from game developers and players alike: the minigame. Usually found in collections of tens or even hundreds of quick, skit-like sub-games in which players complete simple tasks, minigames have proved to be the perfect match for the Wii's more physical control scheme. Of the 10 most popular Wii titles now on Gamefly.com, a Netflix-like service for gamers, four are either entirely or partially based on minigames.

Currently at the top of the list is WarioWare: Smooth Moves, the latest addition (released last week) to the popular WarioWare franchise, all of which are collections of minigames. For WarioWare, though, “micro” seems to be the more appropriate prefix, since most of the individual games last no longer than a few seconds. Presented with the sense of humor and graphic style that can only come from Japanese videogame designers, Smooth Moves requires players to hold the Wii remote in various “forms” (between your fingers like a pencil, touching your nose like an elephant's trunk, etc.) and use it to complete any number of random tasks, from slicing barrels with an imaginary samurai sword to inserting imaginary dentures into an elderly woman's toothless mouth. [See the videos after the jump].

It goes without saying that a room full of people shouting “Grate that cellphone!” or “Interview that polar bear!” while flailing limbs and occasionally leaping up to do squats or a hula dance is, well, a unique scene. After witnessing such a scene, it becomes clear why the most viral of the Wii-related videos to sweep the Net almost always have the lens trained on the players of the games rather than footage of the games themselves.

Only a few months into its life, the Wii has managed to transform the spectacle of playing videogames (more often than not of the mini variety) into a form of entertainment in itself. I think it's safe to say that Nintendo might be on to something big.

For a closer look at WarioWare and the people who play it, click on through... —John Mahoney

## Riding With Foam for Brains

Shortly before our crazy biker pulls the reverse-Knievel—jumping far past the landing area instead of far short—we hear one of his compatriots shout, “You can go twice as fast!” This is a faulty hypothesis, as it turns out, but to the layman it would seem to make sense. After all, our biker had previously executed a graceful flop straight into the giant pit o’ foam. Doubling the takeoff speed intuitively should double the distance he flies, putting him a little farther into the pit but still within its bounds. Right?

Not exactly. Though it’s impossible to tell from the video exactly how much faster the biker was going on the second attempt, any increase in speed would be liable to have unforeseen consequences. That’s because the best way to understand how the bike flies is not with the concept of speed, but with energy. Why? Energy, as the lab coats like to say, is always conserved—and it’s gotta go somewhere. In this case, all the energy the bike carries into the jump is used to lift the bike however many dozen feet into the air before gravity puts it back into the speed of the freefall.

The funny thing about energy, though, is that it increases with the square of speed. That means that an object going twice as fast has four times as much energy, one going three times as fast has nine times as much energy, and so on. And practically speaking, four times as much energy means our biker is going to fly four times as high and sail four times as far. Exponents, like landing distances, tend to increase quickly. It’s important to make sure your foam can accommodate them. —Michael Moyer

Related:

Flight of the Pole Dancer

Shake, Shake Chinook

Crane Overboard!

Goodbye, Moto

Stick That Landing

Yao: Rejected!

Why a Car on Skis Only Jumps So Far

Dude, Where's My Downforce?

Breakin' Circuits: The Electric Boogaloo

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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:
Rebecca Boyle | Email
Kelsey D. Atherton | Email
Francie Diep | Email
Shaunacy Ferro | Email

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