Have you ever watched the movie Cars with Lightning McQueen and Mater? If you have you way have noticed that the movie franchise is largely based on the sport Nascar, in which many cars race around a track to be the first to cross the finish line. As you can imagine the speed at which these cars travel is very important to the racers, but what truly is speed, and how do we measure it?

In Physics we define speed as the rate at which distance changes. It is important to note that when discussing speed it doesn’t matter which direction the object in question is heading. Speed is usually measured in meters per second, but can be any described using any unit of distance divided by any unit of time. This is why most speedometers on cars in the Nascar races describe the speed of the cars in miles per hour.

A unit many physicists use in place of speed however is velocity. Velocity is the rate at which distance changes in a certain direction, and is measured in the change in distance over time similar to speed. The major difference between speed and velocity is the idea that speed exists as a scalar quantity while velocity exists as a vector quantity. A scalar quantity is a quantity is a quantity that can be described by a magnitude quantity while vector quantities are quantities that depend on both magnitude and direction.

Speed and Velocity are important concepts to understand when watching Nascar and other racing sports, and maybe through understanding these concepts you’ll be able to design a faster racing car which can reach speeds that were previously unimaginable.