Two cars approach each other on a straight and level road. Car A is traveling at 75 km/h, due north and car B is traveling at 45 km/h, due south. Both velocities are measured relative to the ground.
-What is the velocity of car A relative to an observer in car B?
A)75 km/h, north
B)30 km/h, north
C)30 km/h, south
D)120 km/h, south
E)120 km/h, north

Question

Quizplus · Accepted Answer

The velocity of car A relative to an observer in car B is the vector sum of the velocity of car A relative to the ground and the velocity of car B relative to the ground. The velocity of car A relative to the ground is 75 km/h, due north, and the velocity of car B relative to the ground is 45 km/h, due south. The vector sum of these two velocities is 120 km/h, due north.

Two Cars Approach Each Other on a Straight and Level