Unit of Velocity - Definition, FAQs
Velocity is an important concept in physics that describes how fast an object moves in a particular direction. Unlike speed, velocity considers both magnitude and direction, which makes it a vector quantity. In this article, you will learn about the SI unit of velocity, which is metre per second (m/s), and understand why it is used as the standard unit in scientific measurements. The article also explains other commonly used units of velocity such as kilometre per hour, mile per hour, knot, and foot per second. Along with this, you will study the dimensional formula of velocity and the clear difference between speed and velocity. This complete guide will help students build strong conceptual understanding for exams and competitive tests.
This Story also Contains
- SI Unit of Velocity
- Some Other Units of Velocity
- Dimension of Velocity
- Difference Between Unit of Speed and Velocity
SI Unit of Velocity
Velocity is defined as the rate of change of displacement with respect to time. It is a vector quantity because it has both magnitude and direction.
In the International System of Units (SI), the unit of displacement is metre (m) and the unit of time is second (s). Therefore, the SI unit of velocity is metre per second (m/s).
When a body covers a displacement of one metre in one second in a given direction, its velocity is said to be one metre per second.
Some Other Units of Velocity
Apart from the SI unit (metre per second), velocity is expressed in several other units depending on practical usage and field of study. Some commonly used units are:
- Kilometre per hour (km/h) – Commonly used for vehicles and road transport.
- Mile per hour (mph) – Used in countries like the United States and United Kingdom.
- Knot – Used in air and sea navigation (1 knot = 1 nautical mile per hour).
- Foot per second (ft/s) – Used in engineering and aviation in some countries.
- Feet per minute (ft/min) – Used for measuring vertical speed (e.g., elevators, aircraft climb rate).
- Metre per hour (m/h) – Used for very slow speeds.
- Inch per second (in/s) – Used in small mechanical systems.
- Speed of light (c) – A special unit used in physics to express very high velocities, especially in modern physics.
Dimension of Velocity
Velocity is defined as the rate of change of displacement with respect to time.
We know that:
- Displacement has the dimension of length (L)
- Time has the dimension of time (T)
Since velocity $=$ displacement $\div$ time,
Dimension of Velocity $=\left[L T^{-1}\right]$
Dimensional Formula of Velocity:
$
\left[M^0 L^1 T^{-1}\right]
$
Also Read:
Difference Between Unit of Speed and Velocity
| Speed | Velocity |
| Speed is the measure of how fastly an object is moving. | the direction of the movement of an object. |
| It is a scalar quantity | It is a vector quantity |
| rate of change of distance | Rate of change of displacement |
| Speed of an object moving is never negative | velocity of a moving object can be zero, positive or negative. |
| indicator of the rapidity of the object. | indicator of the position as well as the rapidity of the object. |
| It can be defined as the distance covered by an object in unit time. | Velocity can be defined as the displacement of the object in unit time. |
Also check-
- NCERT Exemplar Class 11th Physics Solutions
- NCERT Exemplar Class 12th Physics Solutions
- NCERT Exemplar Solutions for All Subjects
NCERT Physics Notes:
Frequently Asked Questions (FAQs)
m/s (ms-1) is the SI unit of velocity.
cm/s (cms-1) is the cgs unit of velocity.
The units for measuring speed and velocity are the same. The metre is the SI unit for measuring distance and displacement. The second is the SI unit of time. The metre per second – the SI unit of speed and velocity
Speed | Velocity |
Speed is the measure of how fastly an object is moving. | the direction of the movement of an object. |
It is a scalar quantity | It is a vector quantity |
rate of change of distance | Rate of change of displacement |
Speed of an object moving is never negative | velocity of a moving object can be zero, positive or negative. |
indicator of the rapidity of the object. | indicator of the position as well as the rapidity of the object. |
It can be defined as the distance covered by an object in unit time. | Velocity can be defined as the displacement of the object in unit time. |
