Question

Srishti runs $18km$ in $2hours$. What is her average speed?

• A. $1.5m{s}^{-1}$
• B. $2.5m{s}^{-1}$
• C. $3.5m{s}^{-1}$
• D. $4.5m{s}^{-1}$

Answer 1

The correct option is B $2.5m{s}^{-1}$

Given:
Distance covered, $d=18km$
Time taken to cover the distance, $t=2h$

From definition,
$\text{Average speed}=\frac{\text{Distance}}{\text{Time}}$
$v=\frac{18km}{2h}=9km{h}^{-1}$

Since $1km=1000m$ and$1h=3600s$
Hence, distance covered in $m{s}^{-1}$ is:
$v=9\times \frac{1000m}{3600s}$
$v=2.5m{s}^{-1}$
Therefore, Srishti's average speed is $2.5m{s}^{-1}$