I'm going to collapse onto the floor.
collapse is good
The balanced structure was so unstable that it could collapse at any moment.
If you do not get off of the table, it will collapse!
the roof collapsed
Mine shafts are often weak and can collapse. After working for 48 hours without a break, he was about to collapse.
The mood of the verb "was about to collapse" in this sentence is indicative mood, as it states a fact or reality about the old shack.
After the earthquake the bridge was unstable, it could collapse at any moment.
The strong wind will make the building collapse.
The mood of the verb in the sentence is indicative. The verb "looked" is stating a fact about the old shack appearing as if it was about to collapse. There is no uncertainty or doubt implied in the statement.
The weight of the snow caused the roof to collapse. Her nervous disposition lead to a total collapse.
Because the drains were blocked with leaves, a heavy downpour caused the roof to collapse. A downpour in the desert can cause flash floods many miles away.
A complex sentence is a sentence that is separated by a conjunctions and a comma and on one side there is a dependent clause and on the other there is a independent.