Acceleration is the rate of change of velocity over time, measured by the change in velocity divided by the time interval over which that change occurs.

Here's how to measure it operationally:

1. Measure the initial velocity (v1) of an object at a specific time (t1).

2. Measure the final velocity (v2) of the object at a later time (t2).

3. Calculate the change in velocity (Δv) by subtracting the initial velocity from the final velocity: Δv = v2 - v1.

4. Calculate the time interval (Δt) by subtracting the initial time from the final time: Δt = t2 - t1.

5. Divide the change in velocity (Δv) by the time interval (Δt) to get the acceleration (a): a = Δv / Δt.

Example:

A car starts from rest (v1 = 0 m/s) and accelerates to a speed of 20 m/s in 5 seconds (Δt = 5 s).

* Δv = 20 m/s - 0 m/s = 20 m/s

* a = 20 m/s / 5 s = 4 m/s²

Therefore, the car's acceleration is 4 meters per second squared (m/s²).