Question

A particle travels half of the distance of a straight journey with a speed $6m/s$. The remaining part of the distance is covered with speed $2m/s$ for half of the time of remaining journey and with speed $4m/s$ for the other half of time. The average speed of the particle is

• A. 3 m / s
• B. 4 m / s
• C. 3 / 4 m / s
• D. 5 m / s

Answer 1

Answer: (B)

From $C$ to $B$ the time interval of travelling is same
So, $v_{av}=\frac{v_2+v_3}{2}=\frac{2+4}{2}=3m/s$

Now, first half is covered with $6m{s}^{-1}$ and second half with $3m{s}^{-1}$.
So when distances are same.
$v_{av}=\frac{2v_1{v}_2}{v_1+v_2}=\frac{2\times 6\times 3}{6+3}=4m{s}^{-1}$
$v_{av}=4m{s}^{-1}$