Final answer:
Brake fade is primarily caused by the conversion of gravitational potential energy into internal energy when brakes overheat, particularly on steep descents. Continuous braking leads to a temperature increase that can cause brake fade. Alternatives like engine braking and regenerative braking can mitigate this issue.
Step-by-step explanation:
The main cause of brake fade at high temperatures is the conversion of gravitational potential energy into internal energy of the truck's brakes during a descent, which raises the temperature of the brake material. The brakes can overheat if this temperature increase happens too quickly, which is particularly likely on steep downhill runs where continuous use of the brakes is necessary. This overheating can cause the brakes to become less efficient or even fail, a phenomenon known as brake fade.
When calculating the temperature increase for 100 kg of brake material, we take into account factors like specific heat, the mass of the truck, and the vertical descent. In the case of engine braking, it utilizes the engine's resistance to avoid this excessive heat buildup in brakes. Hybrid and electric vehicles use regenerative braking systems that convert kinetic energy into electric energy, thus reducing the heating effect on the brake system.