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# Normal Reaction Forces and Weight watch

1. If I say, have an object, of X kg, resting on the ground with no extra forces acting on it, it will have a weight of Xg N downwards, and that same force upwards.

What I don't quite understand is where that Normal Reaction force comes from. I understand that it has to be there because otherwise the object would fall through the ground.. but what causes it?

I know it's an equal and opposite reaction, but to what? If it is the ground responding to weight on it, surely the weight is acting on the ground and not the object? Does weight act on both its object and what it rests on?

I feel i might be missing something really obvious here but I'm so confused.

The more detailed the explanation the more appreciated
2. Well, I just spilt my tea all over my desk, but that isn't necessarily related to this xD

Either ways, in this situation there are two forces acting (for our sake), the reaction force, and the weight of the object, namely the force due to the gravitational field it occupies. It pushes down on the ground with aforementioned weight, and as such, the particles which it pushes on, the dirt, floor, etc, will push back with an equal force, opposite to the direction of the force in the initial situation, so opposite to weight.

I hope I helped! Tell me if you need any more info
3. (Original post by stolenuniverse)
If I say, have an object, of X kg, resting on the ground with no extra forces acting on it, it will have a weight of Xg N downwards, and that same force upwards.

What I don't quite understand is where that Normal Reaction force comes from. I understand that it has to be there because otherwise the object would fall through the ground.. but what causes it?

I know it's an equal and opposite reaction, but to what? If it is the ground responding to weight on it, surely the weight is acting on the ground and not the object? Does weight act on both its object and what it rests on?

I feel i might be missing something really obvious here but I'm so confused.

The more detailed the explanation the more appreciated
Thank you for replying you cleared up half my question 😅 but still my brain experiences confusions
So.. if the force due to gravity causes the object to exert a force on what it's resting on? How does this force affect the object? It's not exerted on the object?? Or is it haha 😅
4. (Original post by stolenuniverse)
Thank you for replying you cleared up half my question 😅 but still my brain experiences confusions
So.. if the force due to gravity causes the object to exert a force on what it's resting on? How does this force affect the object? It's not exerted on the object?? Or is it haha 😅
Well, we need to consider Newtons Third;

If Body A exerts a force on Body B, Body B will exert a force equal to the initial force and opposite to the initial forces direction. I reformed it a little just to make it clear on how this situation may go.

So, Body A being me, and Body B being my wooden floor that my cats dropped a deuce on the one time I let them in my room.

My weight is the force that pushes on the floor, body B, and the floor exerts a force back on me, Body A, the reaction force. The object may itself not budge, but an object doesn't need to necessarily budge, as long as you exert a force on the object the object by Newtons Third must exert a force back on the you, the body that exerted that force.

As for the answer to your question, I'm no chemist, or molecular fellow (I didn't do it, Physics and Biology xD) but all the atoms exert inter-molecular forces that prevent them from moving around too much, they're held in some sort of structure. If you exert a force, you push on that structure, putting shear and/or tension in to it. If you were big enough, the floor would break, after all the bonds wouldn't be able to handle your huge bum anymore (I hope that isn't the case!).

You can see where I'm coming from. The floor may bend ever so slightly, or it may compress a little, but in the end all this action results in a force being exerted back on you, the person who (hopefully) wont break through their ceiling
5. (Original post by Callicious)
Well, we need to consider Newtons Third;

If Body A exerts a force on Body B, Body B will exert a force equal to the initial force and opposite to the initial forces direction. I reformed it a little just to make it clear on how this situation may go.

So, Body A being me, and Body B being my wooden floor that my cats dropped a deuce on the one time I let them in my room.

My weight is the force that pushes on the floor, body B, and the floor exerts a force back on me, Body A, the reaction force. The object may itself not budge, but an object doesn't need to necessarily budge, as long as you exert a force on the object the object by Newtons Third must exert a force back on the you, the body that exerted that force.

As for the answer to your question, I'm no chemist, or molecular fellow (I didn't do it, Physics and Biology xD) but all the atoms exert inter-molecular forces that prevent them from moving around too much, they're held in some sort of structure. If you exert a force, you push on that structure, putting shear and/or tension in to it. If you were big enough, the floor would break, after all the bonds wouldn't be able to handle your huge bum anymore (I hope that isn't the case!).

You can see where I'm coming from. The floor may bend ever so slightly, or it may compress a little, but in the end all this action results in a force being exerted back on you, the person who (hopefully) wont break through their ceiling
Thank you so much!! That must have taken time to write 😜 I appreciate it tho because now I think I get it 😊😊😊
6. (Original post by stolenuniverse)
Thank you so much!! That must have taken time to write 😜 I appreciate it tho because now I think I get it 😊😊😊
No problem! It didn't take that long :P, I think while I type and I can type pretty fast xD

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