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" A Bad Day at the Office Last February, NASCAR driver Clint Bowyer wasn&amp;#039;t thinking about Newtonian physics when his No. 7 Jack Daniel&amp;#039;s Chevrolet flipped over several hundred yards from finishing the Daytona 500. He wasn&amp;#039;t thinking about much of anything: &amp;quot;One second I&amp;#039;m in the clear. Next thing, bam, I&amp;#039;m sliding across the checkered line on my roof.&amp;quot;  Though Bowyer&amp;#039;s experience was gut-wrenching, it was not all that unusual. According to USA Today, there were 1320 wrecks on the NASCAR Cup circuit between 2001 and 2006--that&amp;#039;s about six crashes per race. Bowyer was lucky: He escaped his flip-and-slide relatively unscathed. Such luck is increasingly common in the stock car world, in part because of NASCAR&amp;#039;s efforts to protect its drivers. To understand what the safety gurus are up against, it helps to know a bit about kinetic energy (Ek), which is a measure of how much work--or damage--an object can do in motion. The more massive an object and the faster it&amp;#039;s moving, the more kinetic energy it has. (Ek equals one-half mass times velocity squared, to be precise.) For example, a 3600-pound stock car running at 180 mph has a kinetic energy of 3.9 million ft.-lb. If you were to catapult a 150-pound man into the air with the same energy, he would travel 5 miles. &amp;quot;Safety is all about dissipating energy anywhere other than the driver,&amp;quot; says Diandra Leslie-Pelecky, an associate professor of physics at the University of Nebraska and the author of the new book The Physics of NASCAR. A prolonged wreck like Bowyer&amp;#039;s might look nasty, but it&amp;#039;s actually safer than one that ends in a moment. &amp;quot;Friction between the roof and the track produced heat, sound and sparks, all energy that wasn&amp;#039;t transferred to Bowyer,&amp;quot; Leslie-Pelecky says. Here&amp;#039;s the math: Force equals mass times change in velocity (\u0394v) divided by the time it takes to make that change (\u0394t). NASCAR&amp;#039;s safety improvements aim to reduce the force on the driver&amp;#039;s body both by extending the time it takes for the car to lose velocity, and by immobilizing the driver during the wrenching process. Safer Car NASCAR&amp;#039;s next-generation stock car takes to the track during the 2008 Sprint Cup Series. Although some drivers have complained that the redesigned--and fully mandated--ride is slower than its predecessor&amp;#039;s, all are bullish on the safety enhancements, such as the car&amp;#039;s ability to absorb more energy by crumpling around the driver in a crash. &amp;quot;The car is built so that the area closest to the driver is the strongest,&amp;quot; Leslie-Pelecky says. Here are the highlights:  (Illustration by Transluszent)    A Better Barrier   SAFER Barrier: {a} The outer layer (closest to the track) is made of hollow steel elements, which are strong yet flexible enough to absorb energy during an impact. {b} The middle layer is dense foam, which absorbs energy by compressing. {c} The layer nearest the spectators is made of concrete. No need to change what already works. (Illustration by Transluszent) A critical improvement in recent seasons has been the switch to Steel and Foam Energy Reduction (SAFER) barriers. &amp;quot;Originally, track walls were designed to protect the fans, not drivers, and they&amp;#039;ve done an effective job,&amp;quot; says Steve Peterson, NASCAR&amp;#039;s technical director. But after a series of accidents in 2000, University of Nebraska researchers stepped up efforts to design a wall that would protect drivers without sacrificing fan safety, primarily by dispersing kinetic energy more gradually. &amp;quot;A collision with a SAFER barrier can take twice as long (up to 150 milliseconds) as one with a concrete wall,&amp;quot; Peterson says. &amp;quot;The SAFER wall can absorb 30 to 50 percent of the impact energy.&amp;quot; A Smarter Restraint &amp;amp;gt; The weakest link in a crash is the one between the driver&amp;#039;s head and his body. &amp;quot;People are very much like bobbleheads,&amp;quot; says Dr. John Melvin, one of the world&amp;#039;s top authorities on racing-related injuries. In a wreck, inertia (the tendency of mass to continue moving at a sustained velocity) keeps the body moving forward in the car. The driver&amp;#039;s safety harness (a six-point system of lap and shoulder belts) first stops the pelvis and torso. Unrestrained, the head continues to move forward. Once the neck has extended as far as it can, continued forward momentum causes the fragile bottom of the skull to crack, killing the driver almost instantly. The Head and Neck Support, or HANS, device was created to help eliminate such fatalities. It&amp;#039;s a carbon-fiber and Kevlar collar with two tethers that connect to the driver&amp;#039;s helmet. Upon impact, the device keeps the driver&amp;#039;s head from moving independently of his body. The HANS is so fundamentally simple that its inventor Bob Hubbard built the first prototype at his kitchen table with cardboard and duct tape. Since head-and-neck restraints were mandated in 2001, there hasn&amp;#039;t been a single crash-related NASCAR fatality.  Clint Bowyer&amp;#039;s 2007 Daytona 500 ended when his car was clipped from behind during a chain-reaction crash. The vehicle flipped, skidded 700 ft. and caught on fire--yet Bowyer walked away. (Photograph by Matthew Stockman/Getty Images) "^^<http://www.w3.org/2001/XMLSchema#string>
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