Question

A body moves along a straight track. Half of the distance it covers with a velocity of 40 ms^-1 and the remaining half with a velocity of 60 ms^-1. What is the average velocity for the whole journey?

Answer 1

Let total distance be S.
Body covers distance S/2 with speed 40 ms^-1 then the time taken by him to cover this distance would be T₁ =S/2 X 40.
Again body covers the rest of the distance S/2 with speed 60 ms^-1 then the time taken by him to cover this distance would be T₂ =S/2 X 60.
So total time taken by the body to cover the distance S is T = T₁ + T₂.
Total time T= S/2 (1/40 +1/60) = s(40+60)/2 X 40 X 60 = s/48.
And average speed = S/T = 48 ms^-1.
So average speed is 48 ms^-1.