Feeling the pressure

[Agent Smith]

This is more likely a question in biophysics but there's no such category in the forum and I (probably mis)judged it best to post in the physics forum.   

 

I remember holding a very small metal ball bearing in my palm and feeling its weight, heavy I thought. Then on another occasion I recall holding a piece of wood in my hand, light. I know that its weight, dependent on mass, that we sense. To be held up we need to exert muscular force and we feel the strain in our muscles. 

I was just thinking about this a while ago and realized that the ball bearing being spherical has a smaller area of contact with my palm compared to the chip of wood (flat). Immediately pressure popped to mind. The ball bearing's weight was distributed over a smaller area compared to the wood chip and although my money is on the difference in the sensation in my hands being explicable by mass (wood is lighter than metal), I was wondering if pressure too was being sensed.

[Prajna]

I won't attempt to directly answer your question but something you might like to investigate, which is related, is a much under-recognised sense we have called proprioception (if that's how it's spelt - my spellchecker also 'under-recognises' it.) This sense is not the sense of touch - which we are all familiar with - but the internal sense of e.g. where our limbs are in relation to our body. I hope you will find that an interesting study.

I would say that we certainly sense pressure: you can easily distinguish between a gentle and not so gentle push, for instance. 

[iNow]

It's less about pressure itself and more about how it's focused. Consider pressing the end of a 2x4 into your palm where the mass is interacting with multiple areas of your hand. Now consider doing the same, but instead of a 2x4 it's a toothpick. Both made of wood, but the force is focused into a tighter spot. That makes it perceived as more intense.

Every sensation is just the activation of receptor cells of various flavors and varieties. Those receptors activate a set of electrical impulses across your nervous system, and your brain interprets those signals once they reach it.

A knife and pipe are both made of metal, but pressing them into your palm results in a totally different experience due to how the force is focused vs. spread out. 

[studiot]

3 hours ago, Agent Smith said:

This is more likely a question in biophysics but there's no such category in the forum and I (probably mis)judged it best to post in the physics forum.   

 

I remember holding a very small metal ball bearing in my palm and feeling its weight, heavy I thought. Then on another occasion I recall holding a piece of wood in my hand, light. I know that its weight, dependent on mass, that we sense. To be held up we need to exert muscular force and we feel the strain in our muscles. 

I was just thinking about this a while ago and realized that the ball bearing being spherical has a smaller area of contact with my palm compared to the chip of wood (flat). Immediately pressure popped to mind. The ball bearing's weight was distributed over a smaller area compared to the wood chip and although my money is on the difference in the sensation in my hands being explicable by mass (wood is lighter than metal), I was wondering if pressure too was being sensed.

This is a good topic for you to do some experimentation on your own.

 

For instance you seem to be suggesting that a steel ball felt heavier than a piece of wood.

Take a short length of wood etcf eg a rule

Spread out one hand and lay the rule across all the fingers of that hand.

Now low some fingers, one at a time.

Does the ruler feel any different as you do this ?

 

One thing to remember is that our brain/nervous system receives an enormous amount of sense data.

All our sense data is filtered so that only some reaches the brain.

For instance can you feel the pressure of the ground on your feet ?

[Agent Smith]

Gracias all