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# Newtons second law confusion watch

1. 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?
2. (Original post by JakeRStudent)
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?
Any object will continue it's state of rest or constant velocity in a dead straight line when all if the various forces acting on it remain in that state of equilibrium.

I.e. the forces balance out so that their combined outcome is as if no force is acting on the object.

When the ball hits the wall several things happen:

The ball has kinetic energy by means of it's motion.
The ball is soft and made from an elastic material which can be deformed and can store elastic potential energy.
The wall is thousands of times more massive than the ball.
The wall is dense and bricks are not easily deformed.

The ball will indeed cause the wall to accelerate because the kinetic energy imparted to the wall will change the balance of forces.

However, because of that mass difference together with the softness of the ball, the movement of the wall cannot be noticed by the unaided eye.

The ball does not have anywhere near enough energy to visibly move the wall but the forces applied as a result of the impact are most definitely equal and opposite on BOTH the wall and ball.

It's simply that we cannot perceive the movement but in the wall.

Hit the wall with something more massive and less elastic like a demolition ball on a chain and the action/reaction forces are most definitely observable.
3. (Original post by uberteknik)
Any object will continue it's state of rest or constant velocity in a dead straight line when all if the various forces acting on it remain in that state of equilibrium.

I.e. the forces balance out so that their combined outcome is as if no force is acting on the object.

When the ball hits the wall several things happen:

The ball has kinetic energy by means of it's motion.
The ball is soft and made from an elastic material which can be deformed and can store elastic potential energy.
The wall is thousands of times more massive than the ball.
The wall is dense and bricks are not easily deformed.

The ball will indeed cause the wall to accelerate because the kinetic energy imparted to the wall will change the balance of forces.

However, because of that mass difference together with the softness of the ball, the movement of the wall cannot be noticed by the unaided eye.

The ball does not have anywhere near enough energy to visibly move the wall but the forces applied as a result of the impact are most definitely equal and opposite on BOTH the wall and ball.

It's simply that we cannot perceive the movement but in the wall.

Hit the wall with something more massive and less elastic like a demolition ball on a chain and the action/reaction forces are most definitely observable.
Yes I already understood quite well what you stated. It was just the point about the NSL resulting in the two opposite forces being on the ball and the wall. Resulting in them both accelerating (albeit by whatever small amount). I think I worded this quite badly so I do apologise

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