# Speed and Velocity

## What is speed?

Speed is the rate of change of distance with respect to time.

What is the unit of speed?

The SI unit of speed is meter/second (m/s).

What is the dimension of speed?

The dimension of speed, [v] = LT-1.

## What is instantaneous speed?

Instantaneous speed refers to the speed of a moving body at a certain time (e.g. a certain minute). The rate of change of position of a moving object within an infinitesimal interval of time is called instantaneous speed.

## What do you understand by the speed of a car is 50 kmh-1?

The speed of a car 50 kmh-1 means -

a) The car travel 50 kilometer per hour.

b) The rate of change of position of car is 50 kmh-1. This rate of change in position can happen in both curved and straight line.

## What is velocity?

Velocity is the rate of change of displacement with respect to time.

## What is average velocity?

If a body does not move with uniform velocity, then the velocity obtained by dividing the total displacement by time is called average velocity.

## What is uniform velocity?

If the value and direction of velocity for a moving object remain the same it is uniform velocity.

When a particle travels the same distance every second, then the particle is said to be moving with constant or uniform velocity.

## What is Non-uniform velocity?

If the value and direction or any one of them of velocity for a moving object changes it is non-uniform velocity.

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