How does an automotive braking system primarily reduce speed?

The primary function of an automotive braking system in reducing speed hinges on the conversion of kinetic energy into thermal energy through friction. When you apply the brakes, brake pads press against the brake rotors (or drums), creating friction. This friction generates heat, which dissipates the vehicle's kinetic energy—essentially slowing it down.

As the vehicle's wheels rotate, their kinetic energy must decrease in order for the speed to diminish, and this is accomplished by transforming that energy into heat rather than losing energy in other ways. This process is essential because it ensures that the braking system can repeatedly bring the vehicle to a stop while managing the heat generated to prevent overheating and maintain effective braking performance.

In contrast, increasing tire friction is a factor that can enhance braking effectiveness but doesn't directly describe the method by which speed is reduced. Lowering the vehicle's weight and increasing engine power temporarily are not mechanisms employed by the braking system itself; rather, they may influence overall vehicle performance in other contexts.