Final answer:
Truck brakes used to control speed on a downhill run convert gravitational potential energy into internal energy of the brake material. However, heat transfer issues and the vehicle's mass can affect its effectiveness. Other techniques like engine braking or regenerative braking can be used in such situations.
Step-by-step explanation:
Truck brakes used to control speed on a downhill run do work by converting gravitational potential energy into increased internal energy (higher temperature) of the brake material. This conversion prevents the gravitational potential energy from being converted into kinetic energy of the truck.
The problem with using brakes to control speed on a downhill run is that the mass of the truck is large compared to the brake material, resulting in a rapid increase in temperature that may not transfer enough heat to the environment. This can be a concern when the brakes are used continuously or if there is brake failure.
Instead of relying solely on the brakes, large vehicles that are out of control or have brake failure can use engine braking techniques or regenerative braking systems in hybrid and electric vehicles to help slow down and prevent accidents.