Here's why:

* Acceleration is the rate of change of velocity.

* Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

When a car brakes, its speed decreases. This change in speed means there's a change in velocity. Since there's a change in velocity, there is acceleration.

Important Note: Even though the car is slowing down, the acceleration is in the opposite direction of the car's motion. This is because the car is decelerating, meaning it's accelerating in the opposite direction of its velocity.

Let me know if you'd like more examples!