What distinguishes speed from velocity?

• A. Speed is a ratio of distance to time; velocity includes direction
• B. Speed cannot be negative; velocity can be
• C. Speed is a vector; velocity is a scalar
• D. Speed measures only distance; velocity measures both time and distance

Answer: (A)

The distinction between speed and velocity lies primarily in their definitions. Speed is defined as the rate at which an object covers distance, and it is a scalar quantity, meaning it only has magnitude and no direction. It is calculated as the total distance traveled divided by the time it takes to travel that distance.

On the other hand, velocity is a vector quantity, which means it encompasses both magnitude and direction. When we talk about velocity, we not only state how fast something is moving but also in which direction it is moving. For example, saying a car is traveling at 60 km/h to the north provides a complete description of its velocity, while simply stating 60 km/h gives us only its speed.

In summarizing these definitions, the correct statement that highlights the key difference is that speed is a ratio of distance to time, while velocity incorporates the additional factor of direction. This fundamental difference is crucial in physics, where knowing both speed and direction can significantly impact the analysis of motion and dynamics.