Instantaneous velocity — Science definition
The velocity at a single instant — the value on a speedometer paired with a direction; the slope of a position-time graph at that point.
Where it is taught
- Velocity & Acceleration — Motion & Kinematics, Physics & Environmental Science, Grade 12
In use
That is instantaneous velocity — the velocity at a single instant, which is what a car's speedometer shows (paired with the direction the car is pointing).
Velocity & Acceleration
Questions using instantaneous velocity
Problem 1
Explain the difference between average velocity and instantaneous velocity, using a road trip as your example.
Answer and explanation
Average velocity is the total displacement divided by the total time for the whole trip — it smooths everything into one number, like driving 270 km north in 3 hours for an average velocity of 90 km/h north. Instantaneous velocity is how fast (and which way) you are moving at one specific moment, like the 120 km/h your speedometer reads on the open highway or the 0 km/h at a rest stop. The average can hide big swings in the instantaneous value.