Average-speed-velocity (c2p20) A commuting student leaves home and drives to sch

Question

Average-speed-velocity (c2p20) A commuting student leaves home and drives to school at an average speed of 38.0 km/h. After 22.0 min she realizes that she has forgotten her homework and returns home to get it at the same average speed. It takes 6.0 min to find the report, after which the trip to school 38.0 km away to the east is resumed at the same speed as before What is the average speed for the entire trip? Submit Answer Incorrect. Tries 4/10 Previous Tries What is the average velocity for the entire trip? Submit Answer Tries 0/10 This discussion is closed Send Feedback

Explanation / Answer

speed = 38.0 km/hr

= 38.0*1000 m / 3600 s

= 10.56 m/s

in 1st 22.0 min:

d1 = speed * time

= 10.56 m/s * 22.0*60 s

= 13939 m

Then she takes another 22.0 min to return

d2 = 13939 m

Then she takes 6.0 min to find notes

Finally she travels,

d3 = 38.0 km = 38000 m

t3 = d3/speed

= 38000 m / 10.56 m/s

= 3598 s

= 3598/60 min

= 60.0 min

a)

total distance = 13939 + 13939 + 38000

= 65878 m

= 65.878 km

total time = 22.0 min + 22.0 min + 6.0 min + 60.0 min

= 110 min

= 110/60 hr

= 1.83 hr

average speed = total distance / total time

= 65.878 km / 1.83 hr

= 35.9 km/hr

Answer: 35.9 km/hr

b)

total displacement = 38.0 km

total time = 1.83 hr

average velocity = total displacement / total time

= 38.0 km / 1.83 hr

= 20.8 km/hr

Answer: 20.8 km/hr

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