The change in velocity of an object during a period of time is called acceleration.

Here's a breakdown:

* Velocity: Velocity describes both the speed and direction of an object's motion.

* Acceleration: Acceleration is the rate at which an object's velocity changes over time. It can be a change in speed, a change in direction, or both.

Calculating Acceleration:

You can calculate acceleration using the following formula:

Acceleration (a) = (Final Velocity (vf) - Initial Velocity (vi)) / Time (t)

Example:

Let's say a car starts at rest (vi = 0 m/s) and accelerates to a final velocity of 20 m/s in 5 seconds. The acceleration would be:

a = (20 m/s - 0 m/s) / 5 s = 4 m/s²

This means the car's velocity increases by 4 meters per second every second.