What is Velocity? Units, Formula, Types

Velocity is the rate at which an object changes its position, including both speed and direction. It is a vector quantity.

SI Unit of Velocity,

The SI unit of velocity is meters per second (m/s).

Formula for Velocity,

Velocity is calculated using the formula:

$v = \frac{d}{t}$

Where:

• $v$ = velocity
• $d$ = displacement
• $t$ = time

Velocity is usually measured in metres per second (m/s).

Example,

A car travels 100 metres east in 20 seconds.

$v = \frac{100}{20} = 5\ m/s\ east$

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Types of Velocity

These are the types of velocity:

• Average velocity
• Constant velocity
• Instantaneous velocity
• Uniform velocity
• Angular velocity
• Escape velocity
• Final velocity
• Variable velocity

Average velocity

Average velocity is the total displacement divided by the total time taken. It indicates the overall rate of motion in a specific direction during a journey.

Example,

If a car moves 100 km north in 2 hours, the average velocity is 50 km/h north. It considers both magnitude (speed) and direction.

Average Velocity Formula,

Average Velocity = Total Displacement​ ÷ Total Time

Constant velocity

Constant velocity means an object moves at a steady speed in a straight line. Both the magnitude and direction of motion remain unchanged during the entire motion.

Example,

A train moving at 80 km/h on a straight track without changing speed or direction exhibits constant velocity. Its motion remains uniform throughout.

Constant Velocity Formula,

Constant Velocity = Displacement ÷ ​ Time

Instantaneous velocity

Instantaneous velocity is the velocity of an object at a specific moment in time. It includes both the speed and direction of motion at that exact point.

Example,

A car’s speedometer reading of 60 km/h north at a specific second represents its instantaneous velocity. It shows the current motion details instantly.

Instantaneous Velocity Formula,

Instantaneous Velocity = Displacement​ ÷ Time Interval

Uniform Velocity

Uniform velocity occurs when an object covers equal distances in equal time intervals, maintaining constant speed and direction.

Example,

A train traveling at 50 km/h on a straight track without speed or direction change shows uniform velocity.

Uniform Velocity Formula,

Uniform Velocity = Total Distance ÷ Total Time

Angular Velocity

Angular velocity measures the rate of change of an object’s angular position in a circular path, expressed in radians per second.

Example,

A wheel rotating at 2 radians per second demonstrates angular velocity by completing its rotations steadily over time.

Angular Velocity Formula,

Angular Velocity= θ​ ÷ t

Escape Velocity

Escape velocity is the minimum speed required for an object to break free from a planet’s gravitational pull.

Example,

A rocket needs an escape velocity of 11.2 km/s to leave Earth’s gravitational field and travel into space.

Final Velocity

Final velocity is the velocity an object reaches at the end of a motion or process, considering acceleration and time.

Example,

A car accelerating from 0 to 60 km/h in 5 seconds has a final velocity of 60 km/h.

Final Velocity Formula,

v_f​ = v_i​ + at

Variable Velocity

Variable velocity occurs when an object covers unequal distances in equal time intervals, indicating a change in speed or direction.

Example,

A cyclist speeding up and slowing down while riding through traffic demonstrates variable velocity as motion changes.

Variable Velocity Formula,

v(t) = v₀​+ ∫a(t)dt

Can an object have constant speed but changing velocity?

Yes. If direction changes, velocity changes even when speed stays constant.

Example:

• circular motion

What causes velocity to change?

Velocity changes when:

• speed changes
• direction changes
• acceleration occurs

What is a velocity-time graph?

A velocity-time graph shows how velocity changes over time.

• The slope represents acceleration.
• The area under the graph represents displacement.

Difference Between Speed and Velocity

Aspect	Speed	Velocity
Definition	The rate at which an object moves	The rate of change of position in a given direction
Type	Scalar (only magnitude)	Vector (magnitude + direction)
Example	A car moving at 60 km/h	A car moving 60 km/h north

For example, if a car moves 50 km west, then turns around and moves 50 km east, its total distance is 100 km, but its displacement is 0 km, making its velocity 0 m/s.

Read more What’s the Difference Between Speed and Velocity?

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