A runner runs 2.6 km in 9 min and then takes 30 min to walk back to the starting point.

Question

(a) What is the runner's average velocity for the first 9 min? km/h

(b) What is the average velocity for the time spent walking? km/h

(c) What is the average speed for the whole trip? km/h

Answer 1

(a) average velocity = displacement / time = (2.6 km/9 min) (60 min/1 hour)

The factor (60 min/1 hour) changes the units from km per min to km per hour

 

(b) again, average velocity = displacement / time = (-2.6 km/30 min) (60 min/1 hour)

 

(c) average speed = total distance / total time = (5.2 km / 39 min) (60 min /1 hour)