A lot of writers seem to be using the words "past" and "passed" interchangeably. They are two very different words with very different meanings. It's likely that the use of phonetics in the teaching of English has wrought confusion here as it has so often before.
"Passed" is the past tense of "pass". Hmmm...note that "past" was used to help define "passed". What a grand language English is.
"Pass" and "passed", as verbs, imply movement (from one place to another, one state of being to another, etc.). "Pass the salt and pepper, please." "He passed his math exam."
"Pass" may also be a noun, but as such, still implies a form of movement. See pass for examples.
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"Past" may be a noun, adjective, adverb, or preposition. As a noun or adjective, it always refers to a period of time that has already occurred, the past as contrasted with the present or future.
As an adverb, "past" always implies direction. "I watched him walk past."
As a preposition, "past" always refers to something that is beyond in terms of place, quantity, or time. "His room is the one past mine." "He can't count past twenty." "It's half past nine."
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Hopefully, we can all leave phonetics in the past when we've passed our English test with flying colors.
Your comments, including any disagreement, are welcome.