Final answer:
Velocity is a vector quantity that includes both magnitude and direction, while speed is a scalar quantity, with magnitude only and no direction. Velocity changes when there is a change in speed or direction or both, causing acceleration. Average velocity differs from average speed in that it considers the direction of displacement.
Step-by-step explanation:
Velocity and speed both measure the distance covered over a certain amount of time, yet they differ in a fundamental way. The SI units of both are meters per second (m/s). Velocity is a vector quantity, which means it includes both a magnitude and a direction. In contrast, speed is a scalar quantity, indicating that it has a magnitude but no specific direction associated with it.
The symbol v for velocity is often bold to denote its status as a vector, whereas the symbol for speed is typically italicized since it is a scalar. When discussing velocity changes, it's important to remember that such a change can occur due to a change in speed or direction, or both.
Acceleration occurs when there is a change in velocity. This can be seen when a car turns a corner at a constant speed; the vehicle is accelerating due to the change in direction.
Average speed is calculated as total distance traveled divided by the elapsed time, without regard to the path taken or changes in direction. Average velocity on the other hand, is the displacement divided by the time over which the displacement occurs, and can be positive or negative depending on the sign convention of the direction.