Hello, I've always had the confusion of why there can ever be an unbalanced force on an object causing an acceleration as NSL states "there must be an equal and opposite force of the same type".
However after thinking about this I believe I have developed an understanding of why this is true yet unbalanced forces exist.Say for example a ball collides with a wall and exerts a force F on the wall. My original thinking was that the wall should not accelerate as NSL says the forces will be balanced still. This however is where I was wrong. The wall will accelerate, as too will the ball, as the equal and opposite force is on the ball and NOT the wall. Therefore the forces are unbalanced!
That may be a bit waffley but is my general reasoning correct?