My understanding is that if the car isn't slipping, that static friction at the point of contact between the tyre and the car is what decelerates the car, counteracting the torque which is being applied by the brakes.
This torque is due to kinetic friction (as the rotor has rotational velocity, and the brake pads are held in place) but since this kinetic friction is an internal force / not the net force, do the rotor/brake-pads still heat up? It appears as if they do in the extreme cases (F1 racing), even though the car doesn't appear to be slipping. I'm clearly missing something here.
Best Answer
When braking, the majority of the kinetic energy of the car turns into heat at the brakes.
Here is how it works: when the car slows down its kinetic energy decreases and since we have conservation of energy, this energy needs to go some place.
The brake pads push against the discs. Due to friction between pad and the disc, friction energy is created. This is basically just heat in the discs and the pads.
The contact between tyre and road is really just a mechanism to transfer translational kinetic energy of the car into rotational energy at the wheels. But at first order, it's lossless. All the kinetic energy keeps the disc turning and rubbing against the pads, where it gets turned into heat.
So yes, the discs get hot (and very much so) when you are braking.