Unit of Speed is meters per second or m/s. Speed is a physical quantity that measures the distance travelled by an entity per unit of time. The most commonly used units for speed are meters per second (m/s), kilometres per hour (km/h) and miles per hour (mph). Speed and Velocity are the same physical quantity except for the difference that velocity is a vector quantity and speed is a scalar quantity, so speed and velocity units are the same.

In this article, we will learn the definition of speed, the unit of speed, conversion between units in various systems, sample problems, and frequently asked questions related to the unit of speed.

Definition of Speed

The definition of speed is written as follows,

Speed is the rate of change of distance travelled by an object with respect to the time elapsed.

Speed Formula

Speed is calculated as the ratio of distance travelled to the time taken. Hence, formula of speed is given as

Speed = Distance/Time

What is Unit of Speed?

Unit of Speed is the measurement of magnitude of speed according to defined standard or convention. As the formula of speed is distance travelled per unit time, unit of speed would be the unit of distance per unit of time taken. For convenience, various systems of units have been adopted and units can be converted from one system to another by multiplication with some factor. The S.I. unit of speed is meters per second. The unit of speed depends upon the chosen units of distance and time.

Dimensional Formula for Speed

The dimensional formula for speed is [M⁰ L¹ T^-1]. It can be derived using the formula for speed, i.e. Speed = Distance/Time

Substituting the dimensions for distance and time, we get,

Dimension of Speed = [M⁰L¹T⁰]/[M⁰L⁰T]

Dimension of Speed = [M⁰ L¹ T^-1]

SI Unit of Speed

S.I. unit of speed is meters per second abbreviated as m/s. It can be derived as follows:

• SI unit of distance = meter(m)
• SI unit of time = second(s)

We know that Speed = Distance/Time

Hence, SI unit of Speed = SI unit of Distance/SI unit of Time = meter/second = m/s = ms^-1

Unit of Speed in Other Systems

The unit of speed in different systems is given as follows:

• MKS System: meters per second
• CGS System: centimeters per second
• FPS System: feet per second

What is 1 m/s?

1 m/s represents the speed in which an object covers 1 meter distance in 1 second.

Conversion between Unit of Speed in different Systems

The unit of speed can be converted from one system to another using following relations:

• 1 kilometer per hour = 5/18 meters per second
• 1 centimeter per second = 1/100 meters per second
• 1 foot per second = 0.3048 meters per second
• 1 mile per hour = 0.44704 meters per second

Using the above conversion system we can convert speed of unit from one form to other form

Convert km/h to m/s

To convert km/h to m/s we multiply by 5/18

(km/h) × 5/18 = m/s

For example, convert 60 km/h in m/s

Solution: 60 × 5/18 = 16.66 m/s

Convert m/s to km/h

To convert m/s to km/h we multiply by 18/5

(m/s) × 18/5 = km/h

For example, convert 16.66 m/s in km/h

Solution: 16.66 × 18/5 = 59.976 k/hr approximately equal to 60 km/h

How to Convert SI unit of speed to CGS Unit of speed?

The SI unit of Speed is meters per second and CGS unit of speed is centimeters per second. The conversion can be done as follows:

1 meter = 100 centimeters

1 meter/ 1 sec = 100 centimeters/ 1 sec

or, 1 m/s = 100 cm/s

For example, a speed of 5 m/s in SI units would be 500 cm/s in CGS units.

Facts about Speed

Some facts about speed are listed as follows:

• Speed can never be negative.
• Speed is a scalar quantity which means it has only magnitude but not direction.
• Speed of light in vacuum is 299,792,458 m/s.
• Speed of sound in dry air is 343.2 m/s.
• Escape velocity of earth, i.e. speed required to escape an object from the gravitational pull is 11.2 km/s.