In the sentence:
The cars were destroyed and thrown away in five days.
"were" is the verb, and the noun phrase is simply "the cars" (or you can think of "were destroyed" as a phrasal verb). In any case "were destroyed and thrown away" does not describe "cars" it tells what happened to the cars, so it si not a modifier of the noun "cars". Note that one can form the sentence:
They were destroyed and thrown away in five days.
but the attempted sentences:
- They in five days
- It in five days.
do not work (having no verb), which confirms that "The cars were destroyed and thrown away" is not a noun phrase.
The dog which John loves is dead.
First of all I would recast this as
The dog which John loved is dead.
because the dog is in the past, now being dead. To avoid the tense issue, consider the alternate example:
The dog which John loves is black.
But the point is that "which John loves" (or loved) is a relative clause, telling the reader which particular dog is being discussed. So "The dog which John loves" is a noun phrase. It contains the shorter noun phrase "the dog". Note that the whole noun phrase can be replaced with a single pronoun:
It is black.
and a grammatically valid, albeit not very meaningful, sentence remains.
These wounds require immediate attention by a doctor.
The verb is "require". The noun phrase is "These wounds". Note that this can be replaced by the single pronoun "they":
They require immediate attention by a doctor.
" immediate attention by a doctor" is what the wounds require. That is the object of the verb "require".
A noun phrase does not normally include the main verb of a sentence
Overall and links
If you cannot replace a string of words with a single pronoun and leave a grammatically valid sentence, it is almost surely not a noun phrase. This means that a complete sentence is not normally a noun phrase, nor is an independent clause in a compound sentence.
A noun phrase consists of the primary or head noun and things that modifiy it, such as:
- other nouns used adjectivally ("fallout survival shelter" the head noun is "shelter")
- possessive forms attached to the noun or a shorter npoun phrase ("John's shirt" the head noun is "shirt", "John's" modifies it by indicating which shirt.)
- possessive pronouns
- participles which are function as adjectives ("a flying squirrel" the participle "squirrel" tells the reader what kind of squirrel; "The marching soldiers" "marching" says which soldiers are being referred to, or describes them.)
- prepositional phrases ("a crook on the run" the head noun is "crook" while "on the run tells what the crook is doing, or which crook is meant
- relative clauses that are adjectival in function ("the runner who came in first", the head noun is "runner" )
- Participle phrases ("A politician scheming for a victory")
- infinitives ("A student to teach" the head noun is "student")
Two pages which describe noun phrases in some detail are: