The **speed is the physical magnitude** that shows and expresses the variation in position of an object and as a function of time, which would be the same as saying that it is the distance traveled by an object in the unit of time. But **In addition to time, to define the speed of movement of an object, it will also be necessary to take into account the direction and direction of the aforementioned movement.**.

Therefore, the units to define speed are based on both distance parameters (meters, centimeters, kilometers) and time-related variables (seconds, minutes).

While the most popular unit of speed in the Spanish-speaking world is the kilometer / hour, in the Saxon countries the mile / hour is still used. However, in science with physics or chemistry, it is preferred to use the international system, by which it is suggested to express the speeds in meters / second.

Depending on the length of time traveled, the speed can be of various types: average, instantaneous and relative. The** Average speed **reports the velocity in a given interval and is reached by dividing the displacement by the elapsed time. Consequently, experts often speak of the difference ("delta" in science jargon) between distances and times. Thus, the average speed of a bus will be the result of dividing the distance between the headlands ("delta-space") and the time it took to go from one to another ("delta-time").

On your side,** instantaneous speed **allows us to know the speed of an object that moves along a certain path with the special characteristic that the time lapse is infinitely small, the space it travels is also very small, representing only one point of the aforementioned path. As we can see, it is actually a theoretical concept, widely applied in the hard sciences. Instead, the **relative velocity **between two observers will arise from the value of the velocity of one observer measured by the other. In this way, if 2 vehicles approach each other from the front and one of them travels at 20 km / h and the other at 40 km / h, the relative speed between them will be 60 kh / h. On the contrary, if one of them advances at 100 km / h and another is chasing it at 120 km / h, the relative speed of the second for the first is 20 km / h.

Speed is a widely used concept in the world of sports as well, because a good part of the sports that are practiced, such as soccer, basketball, hockey, tennis, among others, require significant preparation regarding it, since that the resistance achieved at the speed level will largely depend on the success achieved by the athlete in his career. This is even more evident in disciplines such as swimming, athletics, marathon or martial arts.