A car is travelling on a straight line moves with a uniform velocity V₁ for a distance 20m and with a uniform velocity V₂ for the next equal distance. Then the average velocity ‘V’ is given by…

$\text{ Time taken to travel a distance of }20\mathrm{m}\text{ is }{t}_1=\frac{20}{V_1}$

$\text{ Time taken to travel next same distance of }20\text{ is }{t}_2=\frac{20}{V_2}$

$\begin{array}{l}\text{ : Averave velocity }V=\frac{\text{ Total displacement }}{\text{ Total time }}\\ =\frac{20+20}{\left(\frac{20}{V_1}\right)+\left(\frac{20}{V_2}\right)}\\ V=\frac{2}{\left(\frac{1}{V_1}\right)+\left(\frac{1}{V_2}\right)}\end{array}$

$\therefore \frac{2}{V}=\frac{1}{V_1}+\frac{1}{V_2}$