I saw a speeding sedan down the road.
The sedan was speeding down the road.
The first one is an example of the present participle (as the word speeding is linked with the car acting like an adjective) But what about the second case. Is it a use of present participle?
Yes, it is.
According to Merriam-Webster
present participle
a participle that typically expresses present action in relation to the time expressed by the finite verb in its clause and that in English is formed with the suffix -ing and is used in the formation of the progressive tenses
Examples
The verbs dancing in He was dancing and “crying” in “The baby is crying” are present participles.
Yes. The past participle of speeding is "sped". Both these two sentences use an auxiliary verb to put the sentence into the past tense, so "speeding" is correct.
I saw a speeding sedan down the road.
The sedan was speeding down the road.
Without these verbs you would have to use the word "sped".
The sedan sped down the road.
Since the grammar I follow does not distinguish between a gerund and a present participle, "speeding" is referred to as a gerund-participle verb. (You can call it a present participle still.)
Since the grammar I follow distinguishes between category and function, I wouldn't say it "functions like an adjective". It's a gerund-participle that functions as a modifier.
No, the second sentence "The sedan was speeding down the road" is not an example of the present participle. In this sentence, the word "speedy" is used as an adjective to describe the state of the sedan, so it is a simple adjective. The present participle form of a verb is usually used to form continuous tenses and usually ends in "-ing".
