Which statement best distinguishes instantaneous speed from average speed?

• A. Instantaneous speed is the speed over the entire journey.
• B. Instantaneous speed is the speed at the end of the journey.
• C. Instantaneous speed is the speed at the start of the journey.
• D. Instantaneous speed is the speed at a specific moment.

Answer: (D)

Instantaneous speed is the speed at a specific moment in time. This means it can be any value you read on the speedometer at an exact instant, since speed can change as you move.

In contrast, average speed looks at the whole trip: total distance divided by total time. That gives a single value that describes how fast you were on average, even though your speed varied throughout the journey.

So the statement that describes instantaneous speed as the speed at a specific moment is the best fit. The other ideas describe the speed over the entire journey (average speed) or pick a moment like the start or end, which don’t define the general concept of instantaneous speed.