### What is Speed?

Speed is a physical quantity that represents the distance traveled by an object in a certain time interval. For example, if an object has traveled 6 meters in 30 seconds, its speed would be precisely that, 6 meters every 30 seconds. In the International System of Units, the speed is expressed in meters per second (m / s), so this speed would be equal to 0.2 m / s.

One of the mathematical properties of velocity is that it is a vector quantity, which means that it is defined by a **vecto**r and as such the direction of movement must be taken into account. If the direction is not taken into account, in physics one speaks of speed or speed, a scalar magnitude with the same dimensions of space and time as velocity but which is not the vector.

To calculate the speed, simply divide the distance traveled by the elapsed time:

v = s/t

Speed is also used in fields other than motion physics with a similar concept. For example, in chemistry, the rate or rate of reaction is used to measure the rate at which substrates are transformed into products, which also implies a vector direction.

See Also: Difference between Speed and Velocity

### What is Acceleration?

Acceleration is a quantity related to speed since it measures the rate of change of speed in a given period. Continuing with the previous example, if an object travels 6 meters in 30 seconds, its average speed will have been 0.2 m / s, but that does not imply that the object has moved at that speed constantly during the 30 seconds. For one second it has been able to move at 0.4 m / s, and for another second it has been able to carry a speed of 0.1 m / s, although the result is also 6 meters in 30 seconds.

If the object changes speed, that change is measured with acceleration, which is calculated as the difference in speed per unit time (speed/time). For example, if the object goes from rest (speed of 0 m / s) to a speed of 0.2 m / s in 1 second, its acceleration will be 0.2 m / s ^{2} , which means that the speed of the object increases by 0.2 m / s every second. If now the object changes from moving at 0.2 m / s to moving at 0.3 m / s and makes this transition in 2 s, the acceleration will be:

0.3 – 0.2 = 0.1 / 2 = 0.05 m / s ^{2}

This means it increases speed by 0.05 meters every second. You could say that acceleration measures the *rate of change of *velocity. Acceleration can be negative if the speed at the end of the period considered is less than the speed at the beginning, which is known as **deceleration or negative acceleration.**

Acceleration, unlike velocity, does not imply the direction in which an object is moving, so **it is not a vector quantity**. If the object is moving at a constant speed, its acceleration is zero.

### Key differences

- Speed measures the
**rate of movement**of an object, that is, the distance traveled per unit of time. - Acceleration measures the
**rate of change of velocity**, that is, the change in velocity between two different moments.

Related Topics:

- Velocity
- Difference between speed and velocity
- Acceleration formula
- Difference between angular and tangential velocity
- Instantaneous velocity
- Terminal velocity
- Difference between acceleration and velocity