# Kinematics

## Velocity

The velocity of a body is given by the relationship between the displacement of a body at a given time. It can be considered the magnitude that measures how fast a body moves.

Speed ​​analysis is divided into two main topics: average speed and instantaneous speed. It is considered a vector quantity, that is, it has a modulus (numerical value), a direction (Ex .: vertical, horizontal,…) and a direction (Ex .: forward, up,…). However, for elementary problems, where there is displacement in only one direction, the so-called one-dimensional motion, it should be treated as a scalar quantity (with only numerical value).

The commonly adopted speed units are:

m / s (meter per second);

km / h (kilometer per hour);

In the International System (S.I.), the default unit of speed is the m / s. It is therefore important to know how to convert between the km / h it's the m / s, which is given by the following relation: From there, you can extract the following conversion factor: , or equivalent: ## Average speed

Indicates how fast an object moves over an average time interval and is given for the following reason: Where: = Average Speed = Travel range end position - start position ( ) = Time interval end time - start time ( )

For example:
A car travels from Florianópolis - SC to Curitiba - PR. Knowing that the distance between the two cities is 300 km and that the route started at 7 am and ended at noon, calculate the average car speed during the trip: = (end position) - (start position) = (300 km) - (0 km) = 300 km
Is that: = (end time) - (start time) = (12h) - (7h) = 5 h

So:  But if you want to know how fast m / s, just divide this result by 3.6 and you get: 