Life in the fast lane: how scientists are making the world's fastest sport safer.
* Because of its extreme speed during a race, a stock car can become airborne when it rotates during a crash. In 1994, NASCAR introduced roof flaps to stock cars. Whenever a car turns 140 degrees, the flaps flip up. This disrupts the air flow around the car and helps keep the car on the ground.
* A stock car's tires are 20 centimeters (12 inches) wide, don't have treads, and are sticky to the touch. These features help the tires get a better grip on the paved track.
* Compare the shape of NASCAR's stock cars to the car models used in the Indy Racing League and Formula One. What might be some pros and cons to each car shape?
HISTORY: Research the safety measures--both for protecting drivers and spectators--that have been introduced to NASCAR since the sport began in 1948. Then, create a time line showing the improvements over the years.
* Experience the thrill of being behind the wheel of a race car with this IMAX movie, now out on DVD: NASCAR-The IMAX Experience (2004).
* "Tracking Safety," by Daniel McGinn, Newsweek, February 16, 2004.
* How to Drive an Indy Race Car, by David Rubel, John Muir Publications, 1992.
NASCAR driver Ryan Newman keeps his eyes glued on the blur of competitors speeding in front of him. Races can be won and lost by just a few tenths of a second, so he knows that every inch counts in the 805 kilometer (500 mile)-long Daytona 500.
Suddenly, another driver bumps Newman from behind. In an instant, his car is careening out of control. "When you begin to register what's going on, you've already lost control," he says. Newman's Dodge slams into the track's outer barrier, then flips end over end into oncoming racers. The car's rear end nearly rips off before the mangled metal lands upside down in the speedway's grassy infield. As safety crews rush over, Newman crawls out of the window--nearly unharmed.
While Newman escaped his hair-raising crash with only bumps and braises, many NASCAR drivers have not been as lucky. After a string of tragic crashes in 2000 and 2001--including the death of NASCAR superstar Dale Earnhardt--scientists sped into action to try to make racing safer.
Thanks to their efforts, drivers are benefiting from newly designed safety equipment. "[In the last few years] we have had some near-duplicates of fatal crashes from the past. Yet drivers aren't being hurt," says John Melvin, a biomedical engineer who is a safety consultant for the National Association for Stock Car Auto Racing (NASCAR).
Like all NASCAR drivers, Newman races to the checkered flag in a stock car, a vehicle similar to a passenger car. Though it looks like a standard car, it's far from ordinary: Teams of engineers adapt the cars--fine-tuning every inch to maximize speed and control.
The modifications--such as high-powered engines that can cost more than $50,000--help drivers hit speeds topping 322 km (200 mi) per hour. That's near the limit of what the car can handle. "Part of the skill is keeping the car right at the threshold of almost going out of control," says Melvin. "If do that, you'll go faster than the other guys." But pushing the car to the limit is also why even the best drivers--like Newman--sometimes crash.
When a NASCAR driver crashes, massive forces act on the car. One reason: The heavy cars race at an extremely high velocity, or speed in one direction. That means the cars have a lot of momentum and are difficult to stop. So during a wreck, strong forces are applied to the car by the objects it slams into. "We have found that some race cars experience 140 Gs during a crash," says Melvin. That's a force that feels like 140 times the pulling force of gravity.
Luckily for Newman, Daytona's track had recently been fitted with new walls, called SAFER barriers, that helped reduce these pounding forces. "I believe that SAFER barriers have been the biggest improvement in safety in the last 10 years," says Newman. When a car slams into the SAFER barrier, foam blocks in the wall crush--absorbing some of the car's kinetic energy (see Nuts & Bolts, p. 11).
The crushing also stretches out the impact: Instead of the car screeching to a stop in an instant, its kinetic energy is absorbed over a longer period of time. As a result, the magnitude of forces on the driver at any instant is reduced. "If we can double the time of the impact, we can cut the [forces] loaded on the driver in half," says Dean Sicking, an engineer at the University of Nebraska in Lincoln, who helped design the barriers.
But as in many NASCAR accidents, Newman bounced off more than just the speedway's barrier. That's why the stock cars themselves are also designed to absorb energy: The outer part of the car crushes in a crash. The drivers are protected inside the car's inner roll cage, a rigid steel frame that maintains its shape in the event of an accident.
This safety feature falls short, however, when a car is struck on its side. "At the driver's door, the car has only about 15 centimeters (6 inches) of crush distance," says Sicking. To try to prevent injuries in these side-impact crashes, NASCAR scientists are redesigning the cars. One change: The driver's seat will be relocated toward the right, allowing for more crush room--and energy absorption--on the car's left side.
Daytona International Speedway's state-of-the-art barriers and Newman's well-designed vehicle helped to minimize the forces on his car. But he was still in danger--stuck inside his car as it violently flipped across the track. "You have no control at that point," says Newman. "You just rely on the safety equipment in the race car."
According to Newton's first law of motion, when Newman's car slammed into the wall, his body continued flying at a constant velocity until a force--such as his seat belt--acted on it. Over the last few years, NASCAR scientists have improved seat belts to ensure that these forces stop the drivers' bodies safely. "The trick is to evenly distribute the forces about the body in the right places," explains Melvin.
Most drivers now wear 7.6 cm (3 in.)-wide seat belts that include two shoulder straps, a lap belt, and two straps that run between the legs and attach to the back of the seat. That way, the driver stays safely stuck to the seat, and the restraining forces that stop the driver's body from whipping forward are spread evenly across his or her body.
The final and most crucial safety measure Newman sports is a special helmet. During a crash, the inertia of his head could be deadly. His head would tend to keep whipping forward toward the windshield as his body is tightly secured in the seat.
To prevent this neck-threatening motion, scientists designed the so-called HANS head and neck support. This rigid collar wraps around the back of the neck and attaches to a driver's padded helmet and shoulder straps. "It eliminates the whipping motion and tremendously reduces the potential for injury," says Melvin.
With HANS devices and safer seat belts protecting today's drivers, scientists have seen serious NASCAR injuries virtually eliminated. "We will never be able to make racing totally safe," says Sicking. "But we have moved a giant step forward."
KEEP IT STEADY
Most NASCAR teams fill the car's tires with nitrogen gas instead of air. During a race, the tires heat up, causing moisture inside the tires to expand. This expansion can affect the car's handling. Nitrogen contains less moisture than air, so this change in the tires is minimized.
Stock-car windshields are made of Lexan, a strong plastic that can withstand extreme impacts without shattering. If an object flies up during a race, it merely scratches or dents the windshield.
In 2003, NASCAR scientists introduced a new roof exit. The hatch serves as an alternate escape route in case a fire erupts in the car.
Stock-car tires wear out after 120 to 160 km (75 to 100 mi), and the engines burn through a gallon of gasoline in less than 2 minutes. So drivers make pit stops about every 20 minutes. A NASCAR team can change all four tires and fill the car with gas in just 12 to 14 seconds.
Nuts & Bolts
Any moving object has kinetic energy. The amount of this moving energy depends on both the object's mass and its velocity. Moving at 290 km (180 mi) an hour, a 1,542 kilogram (3,400 pound) stock car has about 25 times more kinetic energy than a car of the same weight going 56 km (35 mi) per hour. That means it takes more work, or force exerted over a distance, to stop the race car.
DIRECTIONS: On a separate sheet of paper, use details from the article to help you write the following:
1. You're a NASCAR driver, and you're being interviewed for a television show. Explain to the TV audience how your wide seat belt and the HANS head and neck support help to keep you safe during a crash. Be sure to mention Newton's first law of motion.
2. You are a scientist, and your lab just invented the SAFER barrier. Explain to NASCAR officials how the invention could help reduce injuries to racers in the event of a crash.
Answers will vary, but they should contain the following points:
1. According to Newton's first law of motion, when a race car slams into the wall, the driver's body continues flying at a constant velocity until a force--such as the driver's seat belt--acted on it. To ensure that these forces stop a driver's body safely, scientists have developed seat belts that evenly distribute the forces about the body in the right places. Most drivers now wear 7.6 centimeter (3 inch)-wide seat belts that include two shoulder straps, a lap belt, and two straps that run between the legs and attach to the back of the seat. That way, the driver's body stays safely stuck to the seat and the restraining forces that stop the driver from whipping forward are spread evenly across his or her body. Also, during a crash, inertia would keep whipping the head forward toward the windshield as the body is tightly secured in the seat. The HANS head and neck support has a collar that wraps around the back of the neck and attaches to a driver's padded helmet and shoulder straps. This eliminates the whipping motion and tremendously reduces the potential for injury.
2. When a NASCAR driver crashes, massive forces act on the car. One reason: The heavy cars race at an extremely high velocity. That means the cars have a tot of momentum and are difficult to stop. So during a wreck, strong forces are applied to the car by the object it slams into. Some race cars experience 140 Gs during a crash--a force that feels like 140 times the driver's body weight. SAFER barriers help reduce these pounding forces, When a car slams into the new barrier, foam blocks in the wall crush--absorbing some of the car's kinetic energy. The crushing also stretches out the impact: Instead of the car screeching to a stop in an instant, its kinetic energy is absorbed over a longer period of time. As a result, the magnitude of forces on the driver at any instant is reduced.
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|Title Annotation:||PHYSICAL ENERGY AND MOTION|
|Date:||Oct 24, 2005|
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