Final answer:
The emergency brake system uses mechanical energy to stop the vehicle, along with regenerative braking in some vehicles, which converts energy of motion into electrical energy to slow down the vehicle.
Step-by-step explanation:
In the event of a brake system failure, the emergency brake system uses mechanical energy to stop the vehicle. One common example of this is when the emergency brake lever or pedal is pulled to engage the emergency brake.
Another method used in some vehicles is regenerative braking, which converts the vehicle's energy of motion into electrical energy that can be stored in a battery. This electrical energy can then be used to slow down the vehicle.
Overall, the emergency brake system utilizes various mechanisms to ensure that the vehicle can be brought to a stop safely in the event of brake system failure.