## What is Average Velocity?

It is the total distance travelled in a particular diection divided by total time taken

We can say that

Average Velocity = Total Displacement/Total Time Taken

AVERAGE SPEED FORMULA

Average Speed = Total Distance/Total Time Taken

AVERAGE VELOCITY FORMULA

Average Velocity =Total Displacement/Total Time Taken    Summary

Average Velocity may or may not be equal to Average Speed

## Questions

Q 2 Page 102 - Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?

NCERT Question 2 - Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging (a) from A to B and (b) from A to C?

Example 8.3 - Usha swims in a 90 m long pool. She covers 180 m in one minute by swimming from one end to the other and back along the same straight path. Find the average speed and average Velocity of Usha.

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

Transcript

Example 1 A person travels from Point A to Point B for 30 meters towards south in 4 Seconds. Then he travels from Point B to Point C for 40 Meters towards east in 6 Seconds. What is his Average Speed and Average Velocity? Calculating Average Speed Total Distance Travelled = AB + BC = 30 + 40 = 70 Meters Total Time Taken = 4 + 6 seconds = 10 Seconds Average Speed = (𝑇𝑜𝑡𝑎𝑙 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒)/(𝑇𝑜𝑡𝑎𝑙 𝑇𝑖𝑚𝑒) = 70/10 = 7 m/s Calculating Average Velocity We first need to calculate Total Displacement Displacement = AC Now, Δ ABC is a right angled triangle By Pythagoras Theorem Hypotenuse2 = Height2 + Base2 AC2 = AB2 + BC2 AC2 = 302 + 402 AC2 = 30 × 30 + 40 × 40 AC2 = 9000 + 1600 AC2 = 2500 AC2 = 50 × 50 AC = 50 Meters Thus, Displacement = AC = 50 m towards South East Now, Total Time Taken = 4 + 6 = 10 Seconds Average Velocity = (𝑇𝑜𝑡𝑎𝑙 𝐷𝑖𝑠𝑝𝑙𝑎𝑐𝑒𝑚𝑒𝑛𝑡)/(𝑇𝑜𝑡𝑎𝑙 𝑇𝑖𝑚𝑒) = 50/10 = 5 m/s towards South East

Concepts

Class 9
Chapter 8 Class 9 - Motion 