Question

You drive a car at a speed of $ 70\,\,km\,h^{-1} $ in a straight road for $8.4\, km$, and then the car runs out of petrol. You walk for $30$ min to reach a petrol pump at a distance of $2 \,km$. The average velocity from the beginning of your drive till you reach the petrol pump is

• A. $16.8 \, km\,h^{-1} $
• B. $35 \, km\,h^{-1} $
• C. $64 \, km\,h^{-1} $
• D. $18.6 \, km\,h^{-1} $

Answer 1

Answer: (A)

Here, total distance $=8.4+2=10.4 \,km$
Time $t_{1}=30 \,min =\frac{1}{2} h$
and $t_{2}=\frac{8.4}{70} h$
$ \therefore $ Total time $=\frac{1}{2}+\frac{8.4}{70}=0.12\, h$
Now, average velocity $=\frac{\text { total distance }}{\text { total time }}$
$=\frac{10.4}{0.62}=16.8\, km\, h ^{-1}$