Brain Trust (12 page)

At the end of the day racing comes down to what you’ve got under your hood, right? Not necessarily. When I chatted with Charles Edmondson, physicist at the US Naval Academy and author of the book
Fast Car Physics
, he was fresh back from the track. The truck with his fast car on it hadn’t started, so he’d been forced to borrow a friend’s Neon. Edmondson, who’s also an instructor for road-legal racing, said, “Even with this tiny little four-banger econo-car, I was able to run down all the
students in the intermediate group, including a guy in a turbo Porsche.”

This is because straightaway speed isn’t the crux of racing. It’s how you take a corner that counts.

“Friction’s a finite resource,” says Edmondson. It’s this friction of rubber meeting the road that keeps your car connected to and thus turning around a corner. And using any of this limited friction to brake takes away from the friction available to turn. “Experts do 80 to 90 percent of their braking before they hit the corner,” says Edmondson. Allotting all possible friction to turning instead of braking allows a higher max speed before skidding.

And tires are a neat little physics problem—sure they’re spinning, but as each little panel of the tread hits and grips the road, it becomes momentarily static in regard to the pavement. Because this static friction (the grip something has while sitting still) is so much greater than tires’ kinetic friction (the grip something has when it’s already sliding), the consequence of a small slip tends to be pretty spectacular—a tiny skid slashes a car’s friction limit from static (high) to kinetic (low) and the slide is off to the races, as it were. Commence catastrophic failure and general fiery badness.

But braking early isn’t the end of the story. Next you want to take a racing line. Imagine you can hug the tight inside of a curve or you can go high, riding the curve’s outside arc. Which is best? It turns out it’s nearly a wash—on the inside arc, you’re forced to go slower but the arc is shorter overall; on the outside arc you can go faster but you also have to go further. Either way, you get to the end of the curve at pretty much the same time. So instead of taking the radius your lane gives you, “open up the radius of the turn as much as possible,” says Edmondson. This means starting the turn high, tagging the low point of the inside corner, and then exiting the turn high.

It’s the same in baseball. Frank Morgan, a math professor at

Williams College, showed that if you know you’re going for second, you should immediately widen your path to first to the right of the baseline, allowing you to open up the radius of your turn around the base.

For a single turn, that’s it: Brake before the turn and draw a kind arc.

But now imagine you’re in an S turn (or any set of multiple turns). Exiting the first turn high brings you into the second turn low. That’s bad. And if you’re at your friction limit in the first and late recognizing the danger of a sharper turn in the second, braking only eats up that last little bit of friction, sending you over the static/kinetic threshold and into the wall. That’s really bad.

So the best you can do among multiple turns is to prioritize the tightest turns—set up high coming into tight turns by taking non-optimal lines on the wider turns.

That is, unless you have a straightaway coming up after the last
turn in a set. Because you want to travel as fast as possible over the longest distance possible, you should prioritize this last turn in the set so that the impact of your higher exit speed is magnified across the entire length of the following straightaway.

Puzzle #6:
Racetrack

Because the equation for centripetal force is F = mv
²
÷ r, drawing the longest possible radius means your car feels less force. Draw the racing line that minimizes centripetal force through the course shown below.

Is Superman cool? No. He’s a do-goody Boy Scout in tights and a codpiece. You know who’s cool? General Zod, that’s who. And you can be too.

The easiest thing to destroy with your bare hands is a bridge: They swing.

Like London’s Millennium Bridge, which, under the weight of six hundred people on opening day, June 10, 2000, started to boogie aggressively. There was no wind. And the people weren’t marching in lockstep … at least not at first.

Then, as you can see in the Internet video, “People spread their feet wide and started walking in this hilarious Ministry of Silly Walks kind of way,” says Cornell mathematician Steve Strogatz. Imagine standing in a rowboat. It starts rocking. What do you do? You spread your feet and go with the flow. “And they actually got in step with the vibrations in a way that pumped energy into the bridge,” says Strogatz. This is a positive feedback loop: Strogatz showed that even a slight wobble causes people to synchronize in a way that creates an ever-increasing wobble (causing more people to synchronize, etc.).

And soon synchronicity of disastrous proportions arose spontaneously from randomness, with six hundred people pumping the Millennium Bridge like a swing, while the queen watched in horror.

But what created the first wobble? There are a couple theories, but Steve Strogatz chalks it up to chance: Of the 600 people on the bridge, at some point 301 people put their left foot down as only 299 put down their right. From there, positive feedback was off and running.

You can be that 301st person.

Good ol’ Galloping Gertie, the Tacoma
Narrows Bridge, ripped herself to shreds in 1940 due to aeroelastic flutter: She flapped in the breeze. But unless you were born on Krypton, you simply don’t have the wind power for that kind of thing. Likewise, the Angers Bridge collapsed in 1850 when almost 500 French soldiers marching across the bridge accidentally matched its vertical resonant frequency. But engineers wised up and no modern bridge grooves to the vertical beat of human feet. If you want to crash a bridge, you’ll have to swing it.

Once you have supervillain powers, you’ll need an army of henchmen. Don’t have one? Don’t worry! Science can make one for you.

All you have to do is solve the problem of loyalty.

All organizations struggle to keep people: You help an employee cut her teeth in the business, but the second a more attractive offer comes along, she blows town. Businesses control defection with counteroffers and promotions. But admit it—you’re too cheap to buy a posse. The Mafia has ways of dealing with defection too. But you need the trunk of your car for groceries.

And so the best way for you to keep a posse is with the tried-and-true method of Hamas, Hezbollah, the Taliban, and al-Qaeda: “All of today’s successful terrorist organizations require a signal of commitment,” says University of California–San Diego economist Eli Berman.

This up-front signal of commitment must outweigh the potential gains of later defection. For example, the initiation rite for the Hells Angels includes being peed on by the rest of the gang and then wearing your soaked leathers for a month. Once you’ve spent a month wearing the urine of large, hairy men, the cost you’ve paid to enter the club is higher than any potential gain you could earn by later defecting from it.