whack vs knock

whack and knock both are nouns.

Word	Noun	Adjective	Verb	Adverb
whack	Yes	No	Yes	No
knock	Yes	No	Yes	No

As nouns, whack and knock are synonyms defined as:

Other synonyms of whack include belt, rap, whang.

whack (noun)	knock (noun)
the act of hitting vigorously	the act of hitting vigorously
the sound made by a sharp swift blow	negative criticism
	a vigorous blow
	the sound of knocking (as on a door or in an engine or bearing)
	a bad experience

whack (verb)	knock (verb)
strike hard	find fault with; express criticism of; point out real or perceived flaws
	knock against with force or violence
	rap with the knuckles
	deliver a sharp blow or push
	make light, repeated taps on a surface
	sound like a car engine that is firing too early