An automobile travels on a straight road for 40 km at 30 km/h. it then continues in the same direction for another 40 km at 60 km/h. (a) what is the average velocity of the car during the full 80 km trip? (assume that it moves in the positive x direc

The average velocity is 40km/h.

Explanation:

The average velocity is , where is the distance traveled and the time elapsed.

The distance traveled is clearly 80km since it's all done in the same direction, we only need to know the time elapsed. For this we calculate the time elapsed on the first part, and add it to the time elapsed on the second part using always the formula , where v is the velocity on each part, which is constant.

The time elapsed for the first part is , and the time elapsed for the second part is , giving us a total time of =2h.

Finally, we can calculate the average velocity: .