Final answer:
Speed has no direction and is a scalar quantity, while velocity has both magnitude and direction, making it a vector quantity. Instantaneous speed and average speed also differ since speed measures how fast an object is moving while velocity considers both speed and direction.
Step-by-step explanation:
Speed and velocity are two distinct concepts in physics. One major difference is that speed is a scalar quantity, meaning it has no direction, while velocity is a vector quantity and has both magnitude and direction. For example, if a car is traveling at a speed of 60 miles per hour, that is the magnitude of its velocity, but to fully describe its velocity, we need to include the direction, such as 60 miles per hour north.
Another difference is that speed measures how fast an object is moving, while velocity measures both how fast and in which direction it is moving. This is why we also need to distinguish between instantaneous speed (the speed at a specific instant in time) and average speed (the total distance traveled divided by the elapsed time).