Final answer:
The difference between speed and velocity is that speed is a scalar quantity indicating only how fast an object is moving, whereas velocity is a vector quantity that represents both the speed and direction of the object. Velocity can change with alterations in speed or direction, while speed changes only when the pace of motion changes.
Step-by-step explanation:
The answer to the student's question is d. Velocity is the change in position divided by time, speed simply indicates how fast an object is traveling. To elaborate, speed is a scalar quantity, meaning it only has magnitude. This magnitude is calculated by dividing the distance traveled by the time it took to travel that distance. In other words, it tells us how fast an object is moving without any regard to its direction of motion.
On the other hand, velocity is a vector quantity. It not only informs us about how fast an object is moving but also includes the direction of movement. Hence, the velocity of an object changes not only when the magnitude of its speed changes but also when its direction changes. For instance, when a car turns a corner at a constant speed, its velocity changes due to the change in direction.
It's also important to note that instantaneous speed is the speed at a specific instant in time, while instantaneous velocity is the velocity at a specific instant in time, including both magnitude and direction.