Two cars approach each other; both cars are moving westward, one at 71 km/h, the other at 67 km/h. What is the magnitude of the velocity of the first car relative to (in the frame of reference of) the second car? Answer in units of km/h.

Answer;

= 4 km/hr

Explanation;

All the motion is directed westward, so we can consider west to be positive.

The velocity of the first car relative to the second car is;

Vr = V1 - V2

= 71 km/hr - 67 km/hr

= 4 km/hr

The magnitude of the velocity of the first car relative to the second car is 4 km/hr.