Question

A body covers half the distance with a speed of 20 m/s and the other half with a speed of 30 m/s. The average velocity of the body during the whole journey is :

• A. Zero
• B. 24 $m/s$
• C. 25 $m/s$
• D. None of these

Answer 1

The correct option is B 24 $m/s$

Let the total distance be $2x$.

For first half distance :

Speed is $20m/s$

Thus time taken $t_1=\frac{x}{20}$

For second half distance :

Speed is $30m/s$

Thus time taken $t_2=\frac{x}{30}$

Average velocity $V_{avg}=\frac{2x}{t_1+t_2}$

$⟹V_{avg}=\frac{2x}{\frac{x}{20}+\frac{x}{30}}=\frac{2\times 20\times 30}{20+30}=24m/s$