1. Change in speed: If an object speeds up or slows down, its velocity changes. For example, if a car speeds up from 0 to 60 miles per hour, its velocity changes from 0 to 60 miles per hour.
2. Change in direction: If an object changes direction, its velocity changes. For example, if a ball is thrown straight up into the air and then comes back down, its velocity changes from going up to going down.
3. Change in both speed and direction: If an object changes both its speed and direction, its velocity changes even more. For example, if a car is going 60 miles per hour and turns a corner, its velocity changes to a new speed and a new direction.
The change in velocity can be calculated using the following formula:
```
Δv = vf - vi
```
Where:
* Δv is the change in velocity
* vf is the final velocity
* vi is the initial velocity
