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

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

Tardigrade Admin · Accepted Answer

Here, total distance =8.4+2=10.4 km Time t1=30 min =(1/2) h and t2=(8.4/70) h ∴ Total time =(1/2)+(8.4/70)=0.12 h Now, average velocity =( text total distance / text total time ) =(10.4/0.62)=16.8 km h -1

Q. 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

$16.8 km h^{- 1}$

$35 km h^{- 1}$

$64 km h^{- 1}$

$18.6 km h^{- 1}$

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

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

16.8kmh−1

35kmh−1

64kmh−1

18.6kmh−1