A motorcycle is being driven on a road moving north at 40 miles per hour. A car is driving on the same road moving south at 40 miles per hour. Which of the following is true? a The motorcycle and the car are moving in opposite directions, so their velocities are different. b The motorcycle and car are moving at the same velocity and the same speed. c The motorcycle and car are moving at the same velocity but different speeds. d The motorcycle and the car are moving in opposite directions, so their speeds are different.
a) The motorcycle and the car are moving in opposite directions, so their velocities are different.
Velocity is a vector quantity, which means it has both magnitude and direction. Speed is the magnitude component of velocity. Although the motorcycle and the car have the same speed (40 miles per hour), their velocities are different because they are moving in opposite directions. One is moving north, and the other south. Therefore, the directional components of their velocities are opposite.