Answer :
Final answer:
The emergency relay valve is responsible for applying the brakes on the trailer if it breaks away from the tractor in a dual air brake system.
Explanation:
If the trailer breaks away from the tractor on a dual air brake system, the component that applies the brakes on the trailer is the emergency relay valve. This is critical for the safety of the vehicle and other road users. In a dual air brake system, the trailer has its own air tank and brakes, which are controlled by the emergency relay valve. When a trailer breakaway occurs, the loss of air pressure in the brake line triggers the emergency relay valve to use the air stored in the trailer's tank to apply the brakes, bringing the trailer to a safe stop.
