Question

(19) A car moving over a straight path, covers a distance x with constant speed of
and then
distance with constant speed of V2. Average speed of a car would be .......
​

Answer 1

First x metres covered with v₁. Next x metres covered with v₂.

Avg speed= Total distance/Total time   ---0

TIme for first half:

t₁=d/s

t₁=x/v₁   ---1

Time for second half:

t₂=x/v₂  ---2

Use 2 and 1 in 0:

$avg.speed=\frac{x+x}{\frac{x}{v_1}+\frac{x}{v_2}}\\=\frac{2x}{x\frac{v_2+v_1}{v_1v_2}}\\=\frac{2v_1v_2}{v_2+v_1}$

Hope this helped.