When driving in the mountains, you will often see signs along the street that warn drivers about falling rocks.
A sign warned drivers of falling rocks along the street.
The direct object in this sentence is "us." The verb "warned" is directly affecting "us" by giving them a warning to stay on the ranch.
Warned has no prefixes or suffixes.
The past participle of "warn" is "warned."
The butler was subservient to the needs and demands of the wealthy family.
Despite being warned about his brash behavior, he continued to deviate from the instructions and take unnecessary risks.
The nouns in the sentence are: sign, drivers, rocks, and street.
The verb is "warned." It's the past tense of "to warn." But be advised that some signs do not have verbs at all: they just have fragments like "no passing" or "school zone." And as others on this page have noted, "falling" can be a verb, but in the sentence you asked about, it is not--it's an adjective that describes "rocks."
Drivers were warned of the adverse camber on the bend by the road signage.
Phineus.
jessica always warns me about my future.
The captain warned the lookouts to be extra vigilant as a radio signal warned of possible enemy ships ahead.
The mother warned the daughter not to compromise her values.
The teacher gave a stern reprimand to the students for talking during the test.
The TV weather man warned that a storm, approaching from the west, was imminent.
The commanding officer warned his troops not to pillage the conquered city.
The sign on the highway warned that you must yield to other vehicles.
The soothsayer warned Captain Bob not to travel the Atlantic Ocean for it is stormy.