# Difference Between Speed and Velocity

In everyday use, the terms speed and speed are used interchangeably, thus causing some problems and various confusions; but it is good to know that in science and in mathematics these concepts have different meanings. Difference Between Speed and Velocity

Here we explain what is the difference between speed and speed.

## SPEED  Difference Between Speed and Velocity

In kinematics , speed refers to the rate or rate at which an object covers a distance. It is a scalar quantity. Scalar means that it is used to measure the magnitude or strength of something. In the case of speed, what is measured is the relationship between a distance traveled and the time it takes to travel it. Unlike speed, speed is not vector.

Speed ​​is measured in meters, kilometers, and miles per hour or per second. In the case of air and maritime transport, the “node” is used as a unit and we say (knots per hour).

Galileo Galilei is considered the first person to measure speed by considering the distance traveled by the object. Galileo defines speed as the distance traveled per unit of time.

There are two ways to measure speed: average speed and instantaneous speed. The first is the total distance traveled during the time interval. For example: if a car covers the distance of 320 kilometers over a period of 4 hours, then the average speed would be 80 kilometers per hour (80 km / h).

Average speed does not describe changes in speed that have occurred during the trip, such as traffic stops, speed reduction or acceleration.

On the other hand, the instantaneous speed is the one shown on the speedometer at any given moment. If, while driving, the driver looks at the speedometer, the instantaneous speed will be the speed that it marks at that moment. If a person continues to drive at a speed per hour (example 50 km / h), the instantaneous speed will be considered as well; 50 km / h.

## VELOCITY

Velocity is the rate or rate of change of position of an object, which is equivalent to a specification of its speed and direction of movement. Velocity is a vector quantity. It not only determines the speed of the moving object, but also the direction of the object.

In order to maintain a constant speed, an object must travel in a certain direction for a certain amount of time. If the object changes direction, its speed also changes. In the same sense, it is necessary that the path followed by the object in question is not curved or circular.

An object that moves in a circle and returns to its starting point is said to have zero velocity. For example: a car traveling in a circular circuit at 90 km / h has a speed of 90 km / h; but it doesn’t have a speed.

We speak of vector quantity when knowledge of both the magnitude and the direction of the object is required to be determined. The scalar absolute value (magnitude) of velocity is known as speed. So if there is no direction or heading, it is not about speed, but about speed.

In relation to the above, another example that can be mentioned is the following: a car traveling at 70 km / h in a north direction is said to have a speed of 70 km / h, north.

Speed ​​is commonly used to determine the speed of an object and changes in direction during each point of time that the journey takes place. The change in the rate of velocity as a function of time is known as acceleration , while “deceleration” is known as “negative acceleration” and is written with the sign (  ).

Displacement also plays an important role when determining the speed of an object. The displacement is the shortest distance from the beginning or starting point to the end position or other point.

Key differences between speed and speed

• Speed ​​is a scalar quantity, while velocity is a vector quantity.
• Speed ​​is the rate or rhythm at which an object covers a distance, while speed is the change in position of an object, which is equivalent to a specification of its speed and direction of movement.
• When it comes to speed, the object can change direction and still its average speed will still count. On the other hand, if it is about speed, the object must follow a constant direction; if the direction changes, so does the speed.
• Example of speed : a car traveling at 50 km / h, went from 0 km / h to 30 km / h before reaching 50 km / h; even at some point it could go up to 60. However, the average speed will be counted as the speed of the car (50 km / h).
• Speed ​​example : A car going straight in a particular direction is considered to have a speed. If the car is going north and has an average speed of 30 km / h, it will be said that its speed is 30 km / h, to the north.
• The classic formula for determining speed is: $\ mathbf {\ bar {v}} = \ frac {\ Delta \ mathbf {r}} {\ Delta t}$  where the V  with the hairline above is the average velocity,  Δ r  is the displacement, and  Δt  is the time.
• The classic formula for calculating speed is  V = d / t.