A car is driven between two nearby towns at an average speed of 50 miles/hour. The magnitude of the average velocity of the car
A) will always be the same as the average speed.
B) will always be less than the average speed.
C) will be the same as or greater than the average speed.
D) will be the same as or less than the average speed.
E) will always be greater than the average speed.

Question

Quizplus · Accepted Answer

The average velocity of the car takes into account the direction of travel. If the car travelled in one direction only, the average velocity would be the same as the average speed. However, since the car is travelling between two towns, it has two opposite directions of travel. So, the car's velocity will sometimes be in the same direction as its average speed and sometimes in the opposite direction. This means that sometimes the car's velocity will be greater than its average speed (when it's travelling in the same direction as its average speed) and sometimes it will be less than its average speed (when it's travelling in the opposite direction as its average speed). Therefore, the average velocity could be the same as, greater than, or less than the average speed. The best choice is D since it covers both cases.

A Car Is Driven Between Two Nearby Towns at an Average