Differences between speed and acceleration

When we talk about a moving object, speed and acceleration are two terms that can be commonly used by people. However, physically speaking, we may not know the differences.

Therefore, it is of our particular interest to motivate the correct use of these words through this article, where we are going to briefly define them and then show the most notable differences between them.


The concept of speed can be expressed as a physical magnitude that contemplates the relationship between the space covered by a moving object and the time used for it.

In physics, this magnitude is often expressed in meters per second (m/s), as well as in multiples and submultiples of these. It is also common to use km/h as the number of kilometers traveled in one hour.

For example: If an athlete took 2 hours to travel 15 km, his speed will have been, on average, about 7.5 km/hour, because physically he expresses himself:

Speed= Distance/time = 15km/2h=7.5km/h.


Acceleration can be understood as the action of an object to increase speed in a unit of time. In the international system of units, the acceleration of a body is represented as the speed in meters (m) that a body increases by one second (s) every second (s), resulting in units of meters over seconds squared (m/ s2 ) .

Earth’s gravity is a clear example of acceleration and has a known value of approximately 9.8 m/s 2 depending on where on earth the object is located.

For example:

If we drop an object in free fall from a building, said object will have an acceleration that is based on the value of the acceleration of gravity of the earth, that is, 9.8 m/s 2 as mentioned above, for Therefore, this object will increase its speed by 9.8 m/s every second. Therefore, after 10 seconds, its speed will be 98 m/s, because it is physically expressed:

Velocity = Acceleration x Time = 9.8 m/s 2 x 10s = 98 m/s.

It is also possible to calculate the acceleration if you have the speed and the time through the formula:

Acceleration = Velocity / Time.

As it has been possible to show from the previous definitions and the examples, the speed and acceleration go hand in hand because an object to reach a speed must accelerate and to decrease its speed it must decelerate. Therefore, apart from the differences implicit in the definitions, the following comparative table is presented to summarize the differences between velocity and acceleration:

Speed Acceleration
Velocity is a physical magnitude represented by the relationship between the distance traveled by an object and the time taken to do so. Acceleration is a physical magnitude that expresses the relationship between the increase in speed of an object in the time used for it.
It is centered on the distance an object travels in a time window. It is focused on the change of speed, which increases or decreases, in a time window.
When the speed of a body remains constant. The acceleration is equal to zero or zero.

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