# The Physics of Nascar

 By: Chris DiCicco
 Even though NASCAR started as a backwoods illegal race to run moonshine, it has today evolved into a sport that is not only entertaining but depends on physics too. The obvious element in the physics of NASCAR is the aerodynamic design required by these cars in order to achieve top speeds of near 200 mph with the minimum drag coefficient. But there are other forces involved too such as Newton's Law of Motion and centripetal force. Newton's Law of Motion states that a body will remain in motion unless it is acted upon by some external force. In outer space for example, in the absence of gravity, an object will go on forever. So there are forces that resist the movement of a NASCAR vehicle such as wind drag and another known as centripetal force. Centripetal force should not be confused with centrifugal force. However without getting too technical, you can think of centripetal force as a real force acting perpendicular to the motion of the moving body. Centrifugal force on the other hand is actually a fictitious force and what we feel as we are thrown outward from a moving vehicle is the reaction force. Centripetal force in the physics of NASCAR is crucial to keeping a car on the track. The tires of the vehicle provide the friction which is part of the centripetal force. The centripetal force needed to keep the car on the track cannot exceed the square of the speed of the car. To put it in simple terms, if the car takes a turn too fast, the wheels leave the ground and an accident occurs. The physics of NASCAR dictates that turns on the racetrack must be banked in order to increase the friction (part of the centripetal force) to hold the car.Another component of physics of NASCAR that serves to keep the vehicle with all four wheels on the track during the race is center of gravity. Center of gravity is basically the point where you could balance the car on the top of a flag pole (theoretically). Racing vehicles need low centers of gravity in order to keep the weight close to the track. If a vehicle has a high center of gravity then it can lose control when it hits a turn much faster. Think of an ambulance with a high profile patient area. If the ambulance took a turn too fast, it would topple over. But if its profile was not too high, it could take the turn faster because the center of gravity is lower. An ambulance needs the high profile in order to get patients in and treat them but the physics of NASCAR dictate the low center of gravity in order to apply more centripetal force and keep it attached to the track on a turn. Then there is the machining of engine components in the physics of NASCAR that are important for building horsepower with the minimum of friction. You want friction when it comes to centripetal force but you don't want it inside of an engine. This is why internal engine parts are machined to within very accurate tolerances-much more accurately than automobiles for family and everyday use. Why? It is because you want to minimize friction inside the engine. When engines torque at these speeds, friction is a very dangerous enemy.