What is Velocity?

Velocity is the Rate of change of position. I.e. Rate of displacement with time is called velocity. A velocity of an object is the rate of change of the object’s position with respect to a frame of reference and time, it might sound complicated but velocity is basically speed in a specific direction. It is a vector quantity, which means we need both magnitude and direction to define velocity. The SI unit of it is meter per second (m/ sec) if there is a change in magnitude or the direction in velocity of a body the body is said to be accelerating.

Types of Velocity:

1. Uniform Velocity: A particle is said to have uniform velocity, if magnitudes as well as direction of its velocity remains same and this is possible only when the particles moves in same straight line without reversing its direction.

2. Non – Uniform Velocity: A particle is said to have non – uniform velocity, if either of magnitude or direction of velocity changes.

3. Average Velocity: It is defined as the ratio of displacement to time taken by the body.


\({{\overrightarrow{v}}_{avg}}\,\,=\,\,\frac{\Delta \overrightarrow{r}}{\Delta t}\).

4. Instantaneous Velocity: Instantaneous velocity is defined as rate of change of position vector of particles with time at a certain instant of time.

Instantaneous Velocity \(\overrightarrow{v}\,\,=\,\,\underset{t\to 0}{\mathop{\lim }}\,\,\frac{\Lambda \overrightarrow{r}}{\Delta t}\,\,=\,\,\frac{d\overrightarrow{r}}{dt}\).

How to find Velocity?

Problem: A car travels at uniform velocity a distance of 100 m in 4 seconds. What is the velocity of the car?

Solution: Given,

Distance (d) = 100 m

Time (t) = 4 sec

Velocity of the Car (V) =?

We know that:

\(Velocity(V)\,\,=\,\,\frac{Dis\tan ce(d)}{time(t)}\).

\(Velocity(V)\,\,=\,\,\frac{100\,m}{4\,\sec }\,\,=\,\,25\,m/\sec \).