There’s just something exciting about fast travel. Throughout history, people have always strived to travel faster, whether on foot, horse, boat or bicycle.
Almost every weekend, today’s speed fans can watch their favorite NASCAR driver’s race around the track at dangerous speeds.
Maybe it’s the excitement of the crowd or maybe the constant threat of danger that draws people to the sport. Or perhaps the achievements of science and technology attract some viewers. As a physicist, I love seeing all the principles of physics on display at a NASCAR race.
Speed
NASCAR drivers drive at extremely high speeds, over 200 miles per hour. They accelerate so quickly that it only takes 3-3.5 seconds to go from zero to 100 kilometers per hour. During this acceleration, the car must exert an average of 2,600 pounds of horizontal force on the track. This is comparable to the bite force of a large American alligator or what it takes to lift an adult buffalo.
According to Einstein’s special theory of relativity, the faster you move through space, the slower your time passes. So it’s fair to say that speed demon NASCAR drivers are getting a little older than the rest of us. At the end of the 3.5-hour race, the drivers were about 0.5 nanoseconds younger than the spectators. If a driver drove 200 km/h continuously for the next 50 years, he would age 70 microseconds less than the rest of us.
Because NASCAR drivers are moving at incredibly fast speeds relative to the crowd in the stands, their speeds are reduced from Einstein’s idea, like the speed of a speed light, 670 million mph. The effect of relativity on orbit is small, but it is there.
Rail
So how do drivers achieve these speeds?
When a car comes to a corner, it naturally wants to continue in the direction it was originally traveling. In order to change direction to follow the curve of an oval track, force must be applied.
Friction is the bond between the two that prevents them from sliding against each other.
So for drivers, it’s a balancing act: they want to keep the pedal to the metal, but they can’t corner so fast that their speed exceeds the control provided by friction. Drive too fast and there may not be enough friction to keep the car from continuing in its original direction and sliding straight into the wall. You slow down too much and fall behind the competition.
Track design can help with this. The corners are sloped, meaning they are higher on the outside of the track and lower towards the center. Part of the force of the road pushing the car up—what physicists call the normal force—supports the frictional force of the tires and helps the car turn the corner.
The steepness of the turns on some of the fastest tracks is comparable to the steepness of a playground slide. Banking at Richmond International Raceway allows cars to travel approximately 1.3 times faster than without banking. Wider turns and higher ramps, such as at Daytona and Talladega, allow drivers to maintain higher cornering speeds.
Current
Power is a measure of energy that changes from one form to another over a period of time. In motor sports, this conversion takes place from the chemical energy stored in gasoline into the kinetic energy of movement.
The NASCAR engine produces about 750 horsepower (560 kW), which is more than the equivalent road car model, which makes about 300 horsepower. During a race, the power conversion of a NASCAR engine is approximately 500 times the energy consumption of a typical American household during the same period.
In cars, power comes from burning gas while the engine is running. A NASCAR engine spins 3.5 times faster than a standard road car and is much more efficient, burns faster and produces more horsepower.
Collisions
With the high speed and power of stock cars, there is a risk of dangerous collisions. Some of the heaviest crashes in NASCAR are around 80 Gs, which is 80 times the acceleration of gravity that keeps you on the planet. For perspective, amusement park rides exceed about 6 Gs.
