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If we place something on our head, we can feel it's weight pushing us down. But we ourselves apply normal reaction which balances the weight of the object and stops it from actually pushing us down.

Can we feel our own weight in a similar way ? For that I suppose we would have to feel normal reaction from something we stand on !

I tried 2 things:

  1. Standing up, and I could not really experience any force either in upward or downward direction.

  2. Pushing/Punching a wall and at the instant I felt a force towards the wall and not towards my fist.

I found it a lot weird that you can feel the weight of something kept on your head, but not the normal reaction of the body underneath us! Both the forces are completely balanced and neither is a pseudo but still we can feel only one!

Is there a scientific reason for this observation? Maybe something about normal reaction which I do not know of.

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  • $\begingroup$ Punch the wall until you break your knuckles, that's the normal force. If you usually run the normal force is the responsible of most of the pain. $\endgroup$
    – jinawee
    Commented Feb 1, 2014 at 12:00
  • $\begingroup$ @jinawee : it would take a lousy experimenter to break the apparatus, but it still does not explain while pushing the wall the force felt is towards the wall and not away ! The pain could very well be the result of compression of knucles an indirect result of normal but certainly no direct experience as that observed in placing things on top of ourselves. $\endgroup$ Commented Feb 1, 2014 at 12:15
  • $\begingroup$ I'm starting to think this is more CogSci than Physics. I could not really experience any force either in upward or downward direction. Well I do, maybe my physics knowledge modifies my perception (the problem is that feet are used to the normal force and are less sensitive). The pain could very well be the result of compression the same as the weight on your head. And how do you measure the direction felt of a force? This is neuroscience. $\endgroup$
    – jinawee
    Commented Feb 1, 2014 at 12:35
  • $\begingroup$ Possible duplicate: physics.stackexchange.com/q/46020/2451 $\endgroup$
    – Qmechanic
    Commented Feb 1, 2014 at 15:40
  • $\begingroup$ I can feel it. Maybe you are feeling it but don't know what to look for. Or maybe you need to be more in tune with your body and mind. $\endgroup$
    – Jim
    Commented Aug 1, 2014 at 17:56

4 Answers 4

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I would assume it is was part of evolution that we don really feel it, because it would be very annoying to be continuously aware of the normal force.

However, you can try several things to redistribute the normal force, such that you start to feel it.

  • Try standing on shredded glass. The normal force gets redistributed to a few positions. Would you feel it?
  • Try hanging from a horizontal pole. Sooner or later you'll feel that your muscles are executing a force continuously
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  • $\begingroup$ does not make sense that pressure change makes it observable, also in the 2nd case that has to do with various types of tensile, shearing and bulk stresses and strain cant really pin that tail on normal force $\endgroup$ Commented Feb 1, 2014 at 12:11
  • $\begingroup$ @rijulgupta Why not? Pressure=Force/Area. 2nd,indirectly it is, you wanted to know also if you can feel your own weight (see title) $\endgroup$
    – Bernhard
    Commented Feb 1, 2014 at 12:17
  • $\begingroup$ So the answer is "sometimes" ? $\endgroup$ Commented Feb 1, 2014 at 12:20
  • $\begingroup$ @rijul I would say yes $\endgroup$
    – Bernhard
    Commented Feb 1, 2014 at 12:23
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Here's something quick which you might find helpful to think about. You said:

Pushing/Punching a wall and at the instant I felt a force towards the wall and not towards my fist.

But your fist eventually stopped, didn't it? Therefore, there must have been a force exerted by the wall on your hand which stopped it from continuing forward. If there was no such force, your hand would have continued going all the way through the wall. That's how you experience normal force.

Likewise, when you throw a ball against a wall, at the moment it strikes, it stops and then flings back in the opposite direction. Since $F=ma$, there must have been some force exerted on the ball, which stopped its movement and then flung it back in the opposite direction. That is the normal force.

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  • $\begingroup$ I know what happens ! It is what I was feeling and experiencing that was in question $\endgroup$ Commented Feb 1, 2014 at 16:07
  • $\begingroup$ I guess this is more of a cognition question, then. You're certainly aware that you're exerting a force on the wall because you feel it, but Newtonian forces are reciprocal, so arguably you could also describe it as feeling the wall exerting a force on you. But we're trained since childhood to describe physical manipulations as "you doing something to an object", rather than the reverse, since objects like tools or containers are inanimate. But physics doesn't care about our perceptional biases of who is doing what, it just does what it does. $\endgroup$ Commented Feb 1, 2014 at 16:14
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If you wanna feel what's really happening when you are pushing or applying a force on the wall then the easiest way of doing this is - put yourself (obviously in your head) in place of the wall then if you ( the wall) were not there to support your own force (as human ) then you would have fallen. Another way of doing this is to sit on a bench and then put your self in place of the bench and feel the force that the bench is applying to support you.

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It's an interesting question, some of you have mentioned probably it's because of evolution that our feet got used to it this we don't feel our weight? I think that might not be the case as I've tried standing upside down with my head I still didn't feel my weight.
So what might be the reason we don't feel our weight? Well I think it might have something to do with air in our body. For example throw a stone in water, does it float? No! But when we are much heavier than it, while in a relaxed position can float on the surface. Then again isn't just my speculation, tell your thoughts about it.

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