Yahya A.Sharif
Registered Member
My belly is on the block not touching any bones and the rest of my body is on air. I was able to bear it for a minute with no belly damage. What about putting a rock of my weight 57.7 kg on my belly?
The human body special mass
- Thread starter Yahya A.Sharif
- Start date
The rock stands tip-toe and you gain weight
(
I'm done wasting my time, this was fun for a while but, it is dragging on way to long. I guess physics does not apply to you and you must be magical.
Yahya A.Sharif
Registered Member
The only answer is my theory. I am not magical every one can lie on a concrete block. And everyone knows that putting a 15 kg block " forth the weight 60 kg" let alone a 60 kg rock will damage their belly.
DaveC426913
Valued Senior Member
No. Do the experiment. It will hurt more than you think.
Yahya A.Sharif
Registered Member
Yahya A.Sharif
Registered Member
I challenge you. The only answer is my new theory.
Last edited:
The image on the video looks like parts of your legs and arms are in contact with the sides of the block. That might mean that there are some friction forces applied, meaning that your entire weight is not supported by your stomach. However, that is likely to be a small fraction of your weight.[/QUOTE]
You have several misconceptions, as has previously been pointed out.
Suppose you were to lie on a concrete block that weighs the same as a small car: say 2000 kilograms. The force exerted on your stomach will not then be 2000 kg. Lying on your back with that block (car) on your stomach is not the same situation as lying on your front on top of the block (car).
If you hold an object that has a mass of X kilograms, so that object does not touch the ground, then the downward force on your body due to the object will be equivalent to X kilograms. Hold a 50 kg rock and the downward force on your body due to the rock will be 50 kg. It doesn't matter what your body mass is. It also doesn't matter whether that 50 kg is held in your hands or on your stomach or balanced on your head. The rock will always exert a total downwards force on your body equivalent to 50 kg.
So, why does it feel different holding a 50 kg rock with your hands than it feels when you lie down and place the 50 kg rock on your stomach? Why does it feel different if you balance the 50 kg rock on your head? The reason is that how it feels doesn't just depend on the total force exerted on your body, which, as we have already established, is equivalent to 50 kg in all cases. How it feels also depends on the pressure, which is the force exerted per unit area. The pressure on your body is determined by the total contact area between your body and the rock. In general, a large contact area will have low pressure, while a small contact area will have high pressure. If your 50 kg rock is a large flat slab and you lie on the floor with the rock on your stomach, that 50 kg force will be spread over the whole area of your stomach, resulting in a relatively low pressure. That might mean that it doesn't hurt much, because the compressive force on your stomach per unit area is tolerable. On the other hand, if that 50 kg of rock consists of a long tube of rock and you try to balance that tube with one of its end surfaces (say 2 cm diameter) on the centre of your stomach, then you might rapidly find that your stomach is impaled by a tube of rock, because the resulting pressure (force per unit area) will be much higher. In both cases, though, note that the force is still equivalent to 50 kg.
Consider the following two cases, then:
1. A 50 kg flat slab of rock lies on the ground. You lie across the slab such that only the area of your stomach (say 100 square centimeters) is in contact with slab.
2. You lie on the ground, face up. The same 50 kg slab of rock is placed on your stomach, so that the contact area is the same as in case 1 (100 square centimetres).
In case #2, the force on your stomach will be equivalent to the 50 kg weight of the rock. The pressure will be that force divided by 100 square centimeters.
In case #1, the force on your stomach will be equivalent to your body weight, since in that case your stomach obviously is not supporting the rock; it is supporting your body weight.
If your body mass is 70 kg, then case 2 is going to hurt less than case 1.
If your body mass if 40 kg, then case 2 is going to hurt more than case 1.
Take this to an extreme. Replace the 50 kg rock by a 2000 kg car.
Case 1: you lie on top of the car, bending your body so that only your stomach is in contact. The force your stomach is supporting is your body weight, say 70 kg. You will be able to tolerate this for a time, given the pressure.
Case 2: you lie on the ground and have the 2000 kg car placed on your stomach. In this case, your stomach will need to support 2000 kg of force. Your stomach is not going to come out of this situation very well.
Any questions?
One more case, while we're at it...
Suppose your have a rock with mass exactly equal to your body mass.
Case 1: you lie on top of the rock, touching it only with your stomach.
In this case, your stomach is supporting your entire body mass.
Case 2: you lie on the ground, face up, and the rock is placed on your stomach.
In this case, your stomach is supporting the entire mass of the rock.
In both cases, the force on the stomach is the same, because we said the mass of the rock is the same as the mass of the body. If the contact area is the same in both cases, then the pressure on the stomach will be identical in both cases and things will "feel" identical.
It is a fantasy to imagine that cases 1 and 2 would feel any different, or have different effects on the stomach in this special case where the rock and body masses are the same.
Suppose your have a rock with mass exactly equal to your body mass.
Case 1: you lie on top of the rock, touching it only with your stomach.
In this case, your stomach is supporting your entire body mass.
Case 2: you lie on the ground, face up, and the rock is placed on your stomach.
In this case, your stomach is supporting the entire mass of the rock.
In both cases, the force on the stomach is the same, because we said the mass of the rock is the same as the mass of the body. If the contact area is the same in both cases, then the pressure on the stomach will be identical in both cases and things will "feel" identical.
It is a fantasy to imagine that cases 1 and 2 would feel any different, or have different effects on the stomach in this special case where the rock and body masses are the same.
Yahya A.Sharif
Registered Member
No. My legs do not touch the block nor my arms. AND the areas are equal because putting the block on stomach is just the inverse of lying on the block.
Here is a guy doing the same experiment and showing a picture post #119 he weighs 100 kg. So what about putting a 100 kg rock on a human belly?!
https://www.physicsforums.com/threads/force-to-lift-an-object.1016492/page-4
Yahya A.Sharif
Registered Member
I mean this case. If the pressure is the same why a rock of 57.7 kg will damage my belly, while me lying on my belly as in the video does not affect? The pressure in the belly is not the same for the same area.
This man "post #119 in the link" lies on his belly on only the belly not touching bones. He said he did not suffer . You can try it. I also tried it with little pain that I could bear for 1 minute. The guy on the picture weighs 100+ kg. What will happen if someone puts a rock of 100+ kg on a stool like the picture and put the stool on his belly?
Well, it won't. Either you'll be damaged in both cases, or not, in both cases.
The idea that the two situations would be different is nuts (with all due respect).
If the force is the same, then it has to be. That's physics.
Part of his pelvis appears to be in contact.
Maybe he could bear it for 1 minute, too.
I told you before what would happen. If there's no problem in one case, there'll be no problem in the other case either.
Yahya A.Sharif
Registered Member
So you deny it because it violates physics? So what ? Experiments say so. That what physics is based on.
He said he touched only his belly. So are he and I lying? In such case why you do not try it yourself and give us the results?
You cannot put a rock of 100+ kg on your belly. Can you? No-one can do that, Because you know that it damages your belly.
exchemist
Valued Senior Member
You can stand on a fit person's belly if they tense their abdominal muscles. I have both done it and had it done to me, in my rowing days, just for a laugh. You have no idea what you are talking about. Talk to some sporty friends (if you have any) and they will confirm this or even give you a demonstration.
Yahya A.Sharif
Registered Member
No. Not a sporty person an average human. And not another human. Another human is a different thing. Can you put a rock of your weight on your belly touching no bones?
DaveC426913
Valued Senior Member
The mechanics of soft bodies is a little more complex than everyone is making out. It is a big challenge to try to simulate forces by the body and on the body, because it is both malleable and complex.
Lying on top of a block is not mechanically the same as having a block on your belly. Look here:
1. The pressure is evenly distributed over the entire surface of your belly: That is virtually impossible to do when the box is on top of you. It will rest on a much smaller area, and certainly apply more pressure in certain spots than others.
2. To support your own weight, you are fully tensing and fully contracting all your abdominal muscles. You are in a "crunch". It is virtually impossible not to be: to be relaxed in this position would stop your breathing for one. Fully tensing all your muscles is a lot more difficult when the box is on top of you. For one, you now have to lift your torso, your arms, and your legs right off the floor. Because this is much more difficult, you can't be as effective at distributing the weight of the box evenly over your entire abdomen.
3. Note that you are lying on a cardboard box, which is itself malleable - not a concrete block. That further helps to distribute your weight evenly.
Take away: Face down and face up are mechanically not the same test of the body.
Rest assured though, the inability to get a proper experimental comparison is a shortcoming wrought by your body's complexities; it is not a fault of the physics. And it is certainly not a sign of any supernatural ability of living tissue.
Lying on top of a block is not mechanically the same as having a block on your belly. Look here:
1. The pressure is evenly distributed over the entire surface of your belly: That is virtually impossible to do when the box is on top of you. It will rest on a much smaller area, and certainly apply more pressure in certain spots than others.
2. To support your own weight, you are fully tensing and fully contracting all your abdominal muscles. You are in a "crunch". It is virtually impossible not to be: to be relaxed in this position would stop your breathing for one. Fully tensing all your muscles is a lot more difficult when the box is on top of you. For one, you now have to lift your torso, your arms, and your legs right off the floor. Because this is much more difficult, you can't be as effective at distributing the weight of the box evenly over your entire abdomen.
3. Note that you are lying on a cardboard box, which is itself malleable - not a concrete block. That further helps to distribute your weight evenly.
Take away: Face down and face up are mechanically not the same test of the body.
Rest assured though, the inability to get a proper experimental comparison is a shortcoming wrought by your body's complexities; it is not a fault of the physics. And it is certainly not a sign of any supernatural ability of living tissue.
Last edited:
exchemist
Valued Senior Member
Another human is not a different thing. I certainly could have had a 70kg weight on my belly rather than a 70kg woman. In fact it would have been easier, as a weight would not move about, trying to balance. Here is a video of someone standing on someone else's stomach:
https://www.youtube.com/shorts/MO7XFpXxx24
DaveC426913
Valued Senior Member
Gotta disagree with you on that one buddy.
This thread has suddenly gotten a lot more interesting, and I am of a mind to offer myself in the name of scientific inquiry...
exchemist
Valued Senior Member
Steady on, they were standing on us.Gotta disagree with you on that one buddy.
This thread has suddenly gotten a lot more interesting, and I am of a mind to offer myself in the name of scientific inquiry...
70kg is quite big for a woman, but being rowers they were all pretty fit. As were we. I'm not sure my abdomen would take that weight now, but I am 68. Then, I was in my late 30s.