A cyclist rides 16.0 km east, then 8.0 km west, then 8.0 km east, then 32.0 km west, and finally 11.2 km east. If his average velocity is 24 km/h, how long did it take him to complete the trip? Is this a reasonable time?

a) t = 12 minutes

it takes him 12 minutes to complete the trip.

b) it is not reasonable.

Explanation:

a) Velocity is a vector quantity which is defined as the displacement per unit time.

velocity = displacement/time

time t = displacement / velocity

Let east be the positive x axis.

A cyclist rides 16.0 km east, then 8.0 km west, then 8.0 km east, then 32.0 km west, and finally 11.2 km east

displacement d = 16 - 8 + 8 - 32 + 11.2 = - 4.8km

Velocity = 24km/hr

Time t = |-4.8|/24

t = 0.2 hr * 60 minutes/hr = 12 minutes

t = 12 minutes

it takes him 12 minutes to complete the trip.

b) It is not reasonable because moving at that speed the actual time it will take the cyclists to complete the total distance travelled (75.2km) would be more than 12 minutes.