**Speed definition** – **Speed** is **defined** as the rate at which a particle covers a distance along a given path. It is given by the ratio of distance travelled to the time taken.

**Speed formula**–

**Distance travelled**(s)/

**Time**(t)

**Note**

- Since
**distance travelled**is a**scalar**, the**speed**of a**particle is also**a**scalar**. - The
**unit of speed**is cm s^{-1}in**C.G.S. system**and m s^{-1}in**M.KS.**or**S.I. system**.

## Instantaneous Speed

The

**speed**of a particle at a given**instant**is known as**instantaneous speed**. The**speedometer**of a**vehicle indicates**the**instantaneous speed**of the**vehicle**.

**Uniform Speed**: A body or particle is said to possess

**uniform speed**if it travels equal distances in equal intervals of time.

Consider a person travelling from A to B through O. If he walks at a constant rate of 1 m s

^{-1 }, i.e., for every 1 s if he travels 1 m, then the person is said to possess uniform speed. Uniform speed**indicates**that the**instantaneous speed**of particle remains the same throughout the motion.**Variable speed**: If the

**instantaneous speed**of a particle changes with time, then the body is said to be moving with

**variable speed**.

## Average Speed

**Average speed**: Defined as the ratio of the total distance travelled to the total time taken by the particle to cover that distance.

**Average speed formula =**Total distance/Total time

**Velocity**: It is displacement of a body in unit time or rate of displacement.

**Velocity formula**= displacement/time

**Velocity is a vector quantity**.

**SI unit of velocity**is m s

^{-1}and or

**C.G.S. unit of velocity**is cm s

^{-1}.

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Crystal clear explanation thanks