Question

A body covers one- third of the distance with a velocity $10m{s}^{-1}$ in same direction, the second one-third with a velocity $20m{s}^{-1}$ and the last one third with a velocity of $30m{s}^{-1}$. The average velocity of body is:

• A. $17.8m{s}^{-1}$
• B. $16.4m{s}^{-1}$
• C. $18.3m{s}^{-1}$
• D. $20.2m{s}^{-1}$

Answer 1

The correct option is B $16.4m{s}^{-1}$

We know that average velocity is equal to :$\frac{displacement}{time}$

$\frac{s}{\frac{s}{3.10}+\frac{s}{3.20}+\frac{s}{3.30}}$

$\frac{s}{\frac{s}{30}+\frac{s}{60}+\frac{s}{90}}$

$=\frac{s}{s(\frac{1}{30}+\frac{1}{60}+\frac{1}{90})}$

$=\frac{1}{\frac{6+3+2}{180}}$

$=\frac{1}{\frac{11}{180}}$

$=\frac{180}{11}=16.36$ms${}^{-1}$