# Speed and Velocity

## 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}?

^{-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.