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- Homework Statement
- Hi

I’m having a hard time getting my head around Newtons third law. I’m sorry if this question is long but I thought that by explaining how Iw understand it, and what I’m not understanding, it might be easier for someone to spot exactly what it is I’m not getting what piece of information I’m missing. Also, sorry if my spelling is faulty I am not a native english spacer.

- Relevant Equations
- F=ma

m1a1=m2a2 right?

I have gathered that forces always occur in pairs and are equal in magnitude but opposite in direction and that according to the second law a force is the product of the mas and acceleration of the object exerting the force.

My problem is with getting this make sense with real life examples. If I tow a stone at a stone wall, the force exerted by the stone on the wall is equal to the stones mas times its acceleration. (And by acceleration in this case I take to be the decreasing velocity as the stone comes to a standstill when it hits the wall. Right? ) But does the stone wall change velocity as a consequence of the stone hitting it ? Because if it is not moved by the impact, how can it have an acceleration, and without the acceleration how can it exert a force?

Or maybe it does have an acceleration but in that case it surely must be infinitesimally small so that multiplied even with the walls big mas it should yield a really small force. I am having a hard time believing that the acceleration of the wall can be big enough to make the force exerted from the wall be the same as that exerted from the stone, so I’m clearly missing something!

Another example is if I push on the wall org stand on the ground, as I come to a standstill pushing the wall or standing on the ground, how am I to understand the acceleration if both the wall, the ground and I apparently are not moving?

How am I to mace sense of this?

My problem is with getting this make sense with real life examples. If I tow a stone at a stone wall, the force exerted by the stone on the wall is equal to the stones mas times its acceleration. (And by acceleration in this case I take to be the decreasing velocity as the stone comes to a standstill when it hits the wall. Right? ) But does the stone wall change velocity as a consequence of the stone hitting it ? Because if it is not moved by the impact, how can it have an acceleration, and without the acceleration how can it exert a force?

Or maybe it does have an acceleration but in that case it surely must be infinitesimally small so that multiplied even with the walls big mas it should yield a really small force. I am having a hard time believing that the acceleration of the wall can be big enough to make the force exerted from the wall be the same as that exerted from the stone, so I’m clearly missing something!

Another example is if I push on the wall org stand on the ground, as I come to a standstill pushing the wall or standing on the ground, how am I to understand the acceleration if both the wall, the ground and I apparently are not moving?

How am I to mace sense of this?

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