1. Speed decreases: As you apply the brakes, the car's speed will start to decrease. This is because the brakes are creating friction between the brake pads and the rotors, which slows down the wheels and, in turn, the car.

2. Velocity changes direction: Velocity is a vector quantity, which means it has both magnitude (speed) and direction. When you press the brakes, the direction of the car's velocity will change from forward to backward. This is because the brakes are causing the car to decelerate, or slow down, which means it is moving in the opposite direction of its original motion.

3. Acceleration becomes negative: Acceleration is the rate of change of velocity. When you press the brakes, the car's acceleration becomes negative because the velocity is decreasing. This means the car is slowing down at an increasing rate.

In summary, when you press the brakes, the car's speed decreases, its velocity changes direction, and its acceleration becomes negative.