THE BASICS OF SPEED A dragster engine hums as the vehicle approaches the starting line Crewmembers carefully clean off the rear tires as the car inches forward The crew wants to make sure nothing comes between the tires and the track The wide fat tires are designed to create as much friction or grip on the track as possible When the light turns green the tires will turn the engine’s power into speed on the track Drivers spin their tires before the race to get rid of unwanted substances Crews then brush away extra rubber that has come off the tires 5 CHAPTER ONE
The crew knows that a dragster needs more than a powerful engine to be fast The vehicle that best takes advantage of the laws of motion will win the race Matter in Motion Every race involves objects in motion All of the laws of physics are at work in a race from start to finish Isaac Newton was a physicist who described the basic laws of motion in the 1600s Newton’s first law of motion states that moving objects continue moving at the same speed and 6 IN THE REAL WORLD Setting Speed Limits In the early 1900s the number of motorized vehicles began to increase At first there were no speed limits But early brakes did not always provide force quickly enough to stop the mass of a moving vehicle States and cities soon began setting speed limits to reduce accidents In the 1970s the US government set a nationwide speed limit of 55 miles per hour 89 km h to conserve fuel That law was removed in 1995 Today safer roads and better vehicles allow drivers to travel safely at higher speeds Some states are setting limits as high as 85 miles per hour 137 km h on certain roads
in the same direction until a force causes them to change For example dragsters use parachutes to help them slow down at the end of races Air hitting the parachute provides a force in the opposite direction Newton’s second law of motion says that objects with more mass require more force to move them Mass is the amount of matter in an object Rockets are objects with very large masses It takes a huge force to move a rocket off its launch pad The third law of motion is that every action or force has an 7 The Mass of the Matter People sometimes mistake mass for weight but they are not the same Mass measures the amount of material that makes up an object Weight measures how much gravity acts on an object The weight of an object changes from planet to planet A race car’s mass would not change on Mars But its weight would be less because the gravitational pull is less there If the same car could somehow be taken to Jupiter the car would weigh more than it does on Earth This is because the gravitational pull of Jupiter is much greater than Earth’s
