What is Velocity?

Velocity of body is

Distance travelled by body per unit of time in a given direction

 

Velocity = Distance travelled in a given direction/Time Taken

             = Displacement/Time Taken

 

How is velocity different from speed?

Example 1

Suppose a person travels 6 km in 2 hours towards east

Speed = Distance/Time = 6/2 = 3 km/Hour

Velocity = Displacement/Time = 6/2 = 3 Km/hour towards east

 

Example 2

A car travels 40 km from Delhi to Noida in half an hour towards east

It comes back from Noida to Delhi in another half an hour

Speed = Distance/Time = 80/1 = 80 km/Hour

Velocity = Displacement/Time = 40 - 40/1 = 0/1 = 0

 

Difference between speed and velocity

Speed Velocity
It is Distance travelled by body per unit of time
It is Distance travelled by body per unit of time in a given direction
It only has Magnitude It has Magnitude as well as direction
Formula is Formula is
Speed =Distance/Time Taken Velocity =Distance in a given direction/Time Taken
  =Displacement/Time Taken
Average speed of Moving body is never 0 Average velocity of Moving body can be 0

Note

Are speed and velocity always equal in Magnitude?
No
They may or may not be equal

Example - Speed and Velocity equal in Magnitude

A car travels 40 km from Delhi to Noida in half an hour towards east

Here Speed = Distance/Time = 40/0.5 = 80 Km/Hour

Velocity = Displacement/Time = 40/0.5 = 80 km/hour towards east

Here ,Magnitude of speed and magnitude of velocity are equal(both are 40)

 

Example -Speed and Velocity not equal in Magnitude

A car travels 40 km from Delhi to Noida in half an hour towards east

It comes back from Noida to Delhi in another half an hour

Speed = Distance/Time = 80/1 = 80 km/Hour

Velocity = Displacement/Time = 40 - 40/1 = 0/1 = 0

here,Magnitude of speed is 80 but magnitude of velocity is 0

So both are not equal

 

Summary

Hence,we can say that average speed of moving body can never be 0 but average velocity of moving body can be 0

(Example-In case of Round Trip,there is no displacement,so Displacement is 0,so velocity will also be 0)

 

Questions

Q 1 Page 102 - Distinguish between speed and velocity

View Answer

 

  1. Class 9
  2. Chapter 8 Class 9 - Motion

About the Author

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CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 9 years and a teacher from the past 16 years. He teaches Spoken English, Written English, Grammar and Vocabulary at Englishtan.