Which of the following best describes speed?

Speed is best described as the distance traveled per unit of time. This definition captures the essence of speed as a scalar quantity that reflects how fast an object is moving without taking into account the direction of that motion. It is calculated by dividing the total distance by the time taken to travel that distance.

For instance, if a car travels 100 kilometers in 2 hours, its speed can be calculated as 100 kilometers divided by 2 hours, which equals 50 kilometers per hour. This simple relationship is fundamental in physics and engineering, particularly in fields such as naval operations, where understanding how quickly a vessel can move is crucial for navigation and operational planning.

Other choices mention aspects of motion but do not accurately define speed. For example, the time taken to travel a specific distance focuses only on time without directly linking it to the distance, while velocity incorporates direction, distinguishing it from the concept of speed. Additionally, the rate of change of velocity refers to acceleration rather than speed itself, signifying changes in an object's motion rather than its constant speed. Thus, defining speed as the distance traveled per unit of time provides a clear and straightforward understanding of the term.