Question

a body cover 40m in 20s and next 80m in 20s.Find the average velocity.

Answer 1

Average velocity=total displacement /total time taken
=> avg. Velocity =(40+80)m/(20+20)s
=120m/40s
=3m/s
Hope that helps you :-)

Answer 2

Friend,

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Question: A body cover 40m in 20s and next 80m in 20s. Find the average velocity.

Solution:

What is velocity?
~ Rate of change of position of the object with respect to time is known as velocity.

Formula to calculate velocity 

velocity = $\frac{displacement }{time}$.

Average velocity:
~ It is theof change of total 
distance with respect to the total time taken.

Average velocity = $\frac{total distance }{total time taken}$

So in the above case 
 total distance = 40 + 80 = 120m

Total time = 40s

So average velocity = $\frac{total distance }{total time taken}$

                                 =$\frac{120}{40}$
                                  
                                 = 3m$s^{-1}$

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Hope this helps you

Regards