Concepts of speed, time and distance are familiar from high school. But it is necessary to understand that they are much wider than the basic general education program. And to use a habitual formula, it is necessary to take a set of conditions into account.

## Instruction

1. Taking into account assumptions of classical mechanics, speed characterizes speed of movement of a point in space. It is vector size, that is, speed has the direction. Speed of the movement is usually measured in kilometers per hour or in meters per second (the km/h and m/s respectively is designated).

2. Time in classical mechanics continuous, nothing defined. For measurement a certain periodic sequence of events which is considered a standard of the minimum period is used. This principle is familiar to everyone on the example of ordinary hours. For the solution of elementary physical tasks time is designated seconds (c), minutes (m) or hours (h).

3. The distance is a key concept of many sciences. In a general sense it can be defined as degree of remoteness of objects. In school tasks in physics the distance is usually measured in centimeters (cm), meters (m), kilometers (km), etc.

4. It is necessary to distinguish two concepts: distance between objects and a way which there passes the point, overcoming this distance. When moving the point can move on the shortest distance between points, or perhaps for example, to go on a zigzag trajectory. The distance between points remains the same, and here it will do a way much bigger.

5. Respectively the average speed of movement and average speed of a way differ. For example, for the horse who ran a path, the average speed of a way is other than zero. Whereas the speed of movement is equal to zero as the horse returned to the same point from which began the movement.

6. Average speed of a way is equal to the relation of the way passed by a point at the right time for which the way was passed. It is simple to remember this ratio. Traditionally the distance is designated by letter s (from Latin spatium – "space"), speed – v (English velocity), and time – t (English time). Draw a triangle in which top part distance, and in the basis – time and speed (see the drawing). Now close required size (for example, time). It turns out that time of equally remained fraction – to the distance relation to speed.