knock vs whack

knock and whack both are nouns.

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

As nouns, knock and whack are synonyms defined as:

Other synonyms of knock include belt, rap, whang.

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

knock (verb)	whack (verb)
find fault with; express criticism of; point out real or perceived flaws	strike hard
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