The THIRD LAW is a real ringer.
It looks so trivial, yet it warns us of
a leading cause of confusion in mechanics problems:
There are always two forces for every interaction!
When A exerts a force
on B
there is always an equal and opposite force
exerted back on A by B.
The latter is arbitrarily designated the "reaction force,"
but of course this is only because we first started
talking about the former; both forces have equal intrinsic status.
So if you say, "The force between A and B is...."
I don't know which force you are talking about!
Never talk about "the force" unless you mean "the Force"
from Star Wars.
Always make up a sentence
describing the action taking place:
"The force exerted on [A] by [B] is...."