Question

A commuting student leaves home and drives to school at an average speed of 39.0 km/h. After 23.0 min he realizes that he has forgotten his homework and returns home to get it at the same average speed. It takes 10.0 min to find the report, after which the trip to school 39.0 km away to the east is resumed at the same speed as before. What is the average speed for the entire trip ? What is the average velocity for the entire trip?

Answer 1

Answer:$s_{avg}=\frac{117}{\frac{213}{60}}=32.95 km/h$

$v_{avg}=\frac{39}{\frac{213}{60}}=10.98 km/h$

Explanation:

Given

Distance between home and school is 39 km

Total time taken $=\frac{39}{39}+\frac{23}{60}+\frac{39}{39}+\frac{10}{60}+\frac{39}{39}$

i.e.

$t=3\times 60+23+10=213 min$

Total Distance traveled =39+39+39=117 km

displacement=39 km

Thus Average speed $=\frac{Distance}{Time\ taken}$

$s_{avg}=\frac{117}{\frac{213}{60}}=32.95 km/h$

Average velocity$=\frac{Displacemet}{Time\ taken}$

$v_{avg}=\frac{39\times 60}{213}=10.98 km/h$