70 Racecars-Mid

Racecars FOCUS Question How do the parts of a racecar affect how it moves?

Speed and Direction Zoom! The racecars seem to fly past. They are fast, colorful, and extremely loud! Racecars can be built to go long or short distances. They can be built for different kinds of races. What all racecars have in common is that they are built to go fast, Very, very fast! Racecars that are speeding down the track have a lot of kinetic energy—the energy of motion Speed is how fast something is moving. To describe the speed of something identify the distance it traveled and the time it took. If a racecar travels 56 meters in one second, its speed is 56 meters per second That is about 200 kilometers (125 mi.) per hour. Not all racetracks are straight. Some include turns. When a racecar slows down or turns a corner, its velocity changes. Velocity is the speed that the object travels, combined with the direction it travels.

Kinetic Energy Think about walking around a track. You can measure your speed and velocity as you move. Now think about running on the track as fast as you can. Your speed increases, which means your velocity increases. The faster you run, the more kinetic energy your body has. The faster a racecar goes, the more kinetic energy it has, too. Kinetic energy also depends on the mass of the moving object. If two objects of the same mass are moving at different velocities, the faster one has more kinetic energy. But if two objects of different masses are moving at the same velocity, then the object with larger mass has more kinetic energy. No one would race a dump truck against a racecar. The dump truck needs so much energy to move fast that it cannot compete. Kinetic energy (KE) depends on mass (m) and velocity (v). KE = ½ mv2 Notice that velocity is squared (v2 means v times v) but mass is not. That means a change in velocity affects kinetic energy more than a change in mass will. If the dump truck and racecar are going the same speed. which has more kinetic energy?

From Family Car to Racecar Stock cars, are similar to regular family cars but they are changed, or modified, so that they can go as fast as possible for their mass. In fact, all types of racecars have modifications that make them fast! Spoilers increase downforce. Downforce is a force that pushes the car down. It helps the car stay low to the ground when turning. When a car is aerodynamic. its body is designed to reduce air resistance. Air resistance is the force of the air pushing against an object as the object moves. It slows the car. The tires of a racecar are different than those of a family car. The grip, or traction, between the tires and ground help propel the car forward. Racecar tires are smoother than tires on a regular car to give the racecar better traction on the track.

The engine of a racecar is more powerful than that of a regular car. A stock car's engine can achieve more than 750 horsepower (HP). This is a measurement of how fast the engine can do work, or move the car. A regular car produces about 120 HP. Word Wise Before the invention of the steam engine, most energy for large machines came from horses. The power of the new engines was compared to the number of horses needed to provide the same power. The unit was called one horsepower.

NASCAR Racing The National Association for Stock Car Auto Racing, or NASCAR, is an organization that oversees stock car races. Have you heard of the Daytona 500? It is a famous NASCAR race held in Daytona Beach, Florida. The race is 500 miles long! This means NASCAR vehicles must be designed to drive a long distance in addition to going fast. The racetrack in Daytona is 2.5 miles long and shaped like an oval. Drivers make 200 laps of the course (500 miles). In some years the winners have averaged more than 175 mph for the race, finishing in less than 3 hours of actual racing time.