Speedometers have been standard equipment in automobiles since 1910. For most cars, a pointer indicates the speed on a dial.
Speedometers do not measure velocity. Velocity indicates how fast something is changing position. It is a "vector quantity," which means it involves two measurements. Both an object's speed and its direction are included in velocity. For instance, a car traveling from New York to California might have a speed of 55 mph. However, its velocity is 55 mph, west.Learn more about Car Parts & Maintenance