Final answer:
When a train operator applies the brakes and holds them without releasing until the train comes to a stop, the train will stop abruptly.
Step-by-step explanation:
When a train operator makes a brake application and holds it without increasing or graduating off until the train comes to a stop, the result is ALMOST sure to be the train will stop abruptly. This is because when the brakes are applied and held without releasing, the train's wheels will experience a high amount of static friction with the tracks, causing the train to come to a sudden stop.
The force of friction between two surfaces depends on the normal force between them. In this case, the normal force is the weight of the train pressing down on the tracks. As long as the brakes are engaged, static friction between the train's wheels and the tracks prevents the train from moving. However, when the train comes to a stop, the friction is abruptly released and the train stops suddenly.