Question

A car takes 4 hrs to travel from Bangalore to Chennai whereas the flight takes only 30 min to travel from Bangalore to Chennai. The distance from Bangalore to Chennai by road is 400 km and by air is 150 km. Assume flight path to be straight.

Answer in the given order (in $kmh{r}^{-1}$):

Find the average speed of flight, average velocity of flight, average speed of car, average velocity of car.

• A. 300 , 300, 37.5 , 100
• B. 300 , 37.5, 100 , 100
• C. 300, 300, 200, 100
• D. 300, 300, 100, 37.5

Answer 1

The correct option is D

300, 300, 100, 37.5

Given:
Distance travelled by car, $d_c=400km$
Time taken by car, $t_c=4hrs$
Distance travelled by flight, $d_p=150km$
Time taken by flight, $t_c=30min=1/2hr$

Since flight path is approximated to be straight, it can be taken to be equal to displacement between Bangalore and Chennai.
Hence, displacement of car and displacement of flight is:
$s=150km$

Average speed is defined as the ratio of the total distance covered to the total time taken.
Average velocity is defined as the ratio of the displacement to the total time taken.

Average speed of flight:
$v_p=\frac{150}{1/2}=300kmh{r}^{-1}$

Average velocity of flight:
$v_p^{\prime }=\frac{150}{1/2}=300kmh{r}^{-1}$

Average speed of car:
$v_c=\frac{400}{4}=100kmh{r}^{-1}$

Average velocity of car:
$v_c^{\prime }=\frac{150}{4}=37.5kmh{r}^{-1}$