Physics

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: