Question

4. A particle moves along x-axis with speed
6 m/s for the first half distance of a journey and the
second half distance with a speed 3 m/s. The
average speed in the total journey is
(1) 5 m/s
(2) 4.5 m/s
(3) 4 m/s
(4) 2 m/s
​

Answer 1

6 +3/2 average will be 4.5m/s

Answer 2

A particle travels 6m/s - half of distance ( d/2)
Again travels 3m/s - next half of distance (d/2)

So, we observe d/2 as common for both

So, distance is same

We then see the formula
Av.Sp = 2v1v2/v1+v2
= 2×6×3/6+3
= 36/9
=4 m/s