passing ship boring/bored - The movie was boring. We were bored (result), so we left. With each boring movie, the studio's reputation dropped. With each bored moviegoer, the studio's reputation dropped. passing/passed - The ship was passing. We hoped to be rescued. With each passing ship, we hoped to be rescued.

DavidK gave some good information. Passing and passed are participles functioning as adjectives here. (See below for passing as a gerund.) Using failing and failed: - The failing student was given the opportunity to retake his failed exam. Using passing and passed: - The passing motorcycle nearly collided with the passed car. For a deeper analysis, passing can be a participle or a gerund. - Passing the other vehicles, the fire truck headed for the fire. (passing = present participle as an adverb) - The passing fire truck headed for the fire. (passing = present participle as an adjective) - Passing other vehicles is unsafe when visibility is poor. (passing = gerund; other vehicles = gerund object; passing other vehicles = subject of "is unsafe")

And while we're giving grammar lessons, it's worth pointing out that there's a third thing that 'passing' can be. In addition to the present participle (as in the original example) and a gerund (as in Chris's last example), the '..ing' form can also be a verbal noun. An example of a verbal noun is 'We barely noticed the passing of time'. Here, the 'ing' form is a fully-functioning noun, complete with an article. And one final titbit... Gerunds and present participles actually used to be pronounced differently from each other: there was a time when the present participle would have been pronounced 'passin' rather than 'passing', so the difference would have been clearer. We probably wouldn't have been having this conversation if they hadn't ended up sounding the same.

You've been given some good answers, Sacha, but - in spite of what some other people have said - you might want to note that 'passing' is a PRESENT PARTICIPLE here, not a gerund. Gerunds function as nouns, while participles (both past and present) can function as adjectives. Here we have a participle functioning as an adjective.

Chris gives a good answer to your question but I wanted to add that “passed” can be an adjective. A “passed ball” is a statistic kept in baseball, for example. Many verbs will be used in such a way, especially in speech. In this case, it rarely happens because it would sound the same as “past”, a common adjective with a different meaning. “I have to retake my failed exam” (Not the most correct, but wouldn’t shock anyone. But you wouldn’t hear “passed exam” because it would be interpreted as “past exam”)