Answer:
Say a 14 year old girl was at a construction site and she was asked to move something like a 10,000 pound brick( one brick). She would be acting on it as the unbalanced force but they would still not change their position.
so to say the girl would be doing everything she could to move that brick but the brick would still be in that same spot so the unbalanced force (the girl) would be acting on the thing that was at rest but it wouldn't move.
so the unbalanced force would not really be acting on the thing at rest; even though the unbalanced force was doing something to the brick.
( just think about it and you will eventually get it...just imagine in your head...)
Explanation:
