The human body special mass

[Yahya A.Sharif]

Of course it's bigger! You are forgetting about the 60 kgf of your body.
When you are standing still on the scale your feet are supporting your weight or a force of 60 kgf. There is also a normal force of 60 kgf 'pushing' upwards against your feet. You don't move because the forces balance out. Standing is not very tiring because the force is mostly supported by your bones and not so much your muscles. This is why standing for 10 minutes is not tiring, however if you raise your heels up just a couple of cm your calf muscles will get tired in 10 minutes since they are now supporting the 60 kgf.

When you raise up on the balls of your feet how much force do your calf muscles feel? When standing with your heels just off of the scale your calf muscles have to balance the 60 kgf from you weight. To move up wards your calf muscles must supply some additional force. If we assume you move the distance very slowly this additional force is 1.5 kgf. So the force that your calf muscles are working against is 61.5 kgf not 1.5 kgf.
.

How? If I exert 60+1.5 kgf by my calf muscles we will have two independent forces one is the force by my calf muscles 60+1.5 kgf and the other is the gravity force by the human mass 60 kgf a total reading by the scale of 60+60+1.5 kgf

 

[Yahya A.Sharif]

This is getting really silly now. It's obvious that human beings can lift a mass greater than their body weight. Look, here's a video of a man lifting 120kg:

https://www.youtube.com/shorts/8-bbxuAAlHg

I did not say a human cannot I said an average human cannot.

 

[Kristoffer]

I did not say a human cannot I said an average human cannot.

Your average human can most definitely lift quite a lot more than you give it credit for.
Last year I pulled a drunk guy that was heavier than me out of a harbour
Do yourself a favour and learn how to apply simple maths and physics
You've been given a clue earlier in the thread how to go about it

 

[origin]

If I exert 60+1.5 kgf by my calf muscles we will have two independent forces one is the force by my calf muscles 60+1.5 kgf and the other is the gravity force by the human mass 60 kgf a total reading by the scale of 60+60+1.5 kgf

Seriously? We just went over the analysis I did and you found no errors, so we agreed that the force on the scale would read (about) 60 + 1.5 kgf.
If you stood on your toes and the scale actually read 120+ kgf that would mean that when you stood on your toes you would shoot into the air a bit. You really don't seem to get the concept of forces balances.
You really need to look up term free body diagram, I think that may help you.

 

[Michael 345]

Has anyone ANYONE asked

I.

WHY the human body has this "special" mass?

 

[origin]

WHY the human body has this "special" mass?

He thinks if you are on a scale, when you stand on your toes that the scale should read twice your weight. Since that doesn't happen he thinks the human body has special mass. Of course a scale should not read twice your weight but he cannot quite grasp this fact.

 

[Michael 345]

He thinks if you are on a scale, when you stand on your toes that the scale should read twice your weight. Since that doesn't happen he thinks the human body has special mass. Of course a scale should not read twice your weight but he cannot quite grasp this fact.

Thanks - makes the whole thread as clear as mud

So where do you find these people with toes which adjust your weight?

 

[Yahya A.Sharif]

Seriously? We just went over the analysis I did and you found no errors, so we agreed that the force on the scale would read (about) 60 + 1.5 kgf.
If you stood on your toes and the scale actually read 120+ kgf that would mean that when you stood on your toes you would shoot into the air a bit. You really don't seem to get the concept of forces balances.
You really need to look up term free body diagram, I think that may help you.

The scale reads 60+1.5 kgf, but why? there are two independent forces one is the human weight 60 kgf adding to it a force the human presses the scale with which you said should be 60+1.5 kgf this is a total of 60+60+1.5 kgf. This is because you say the human exerts 60+1.5 kgf but the human actually exerts only 1.5 kgf adding to it his weight 60 kgf a total of 60+1.5 kgf which the scale reads.

 

[origin]

The scale reads 60+1.5 kgf, but why?

Because that is how physics works. This is exactly what you would expect the scale to read.

there are two independent forces one is the human weight 60 kgf adding to it a force the human presses the scale

No, no, no, you are counting the same force twice. The human weight of 60 kgf is the same force that presses on the scale. Why in the world would you count the same force twice?

 

[James R]

Yahya:

Scales are not magical things. A scale records the contact force that is applied to it. Put a set of bathroom scales against a vertical wall and push on them. They will register a "weight", even though there is no weight force being applied (weights fall downwards, not towards walls).

When a 60 kg human stands on some bathroom scales, the Earth's gravity pulls down on the human with a force equivalent to 60 kg. He would sink into the ground due to that force, except that something is stopping that from happening: the scales are in the way. The result is that the human doesn't move down because the scales apply an upwards force on the human, equivalent to 60 kg.

The scales also have gravity on them, of course. They don't sink into the ground because there's something else in the way: the ground! The ground provides an upwards force on the scales equivalent to the 60 kg weight of the human plus the weight of the scales themselves.

The thing that puzzles me is that I essentially explained all of this to you back on page 1 of this thread. Yet you are still confused. Why?

 

[Yahya A.Sharif]

No, no, no, you are counting the same force twice. The human weight of 60 kgf is the same force that presses on the scale. Why in the world would you count the same force twice?

They are not the same forces. One is gravity force by your body mass, the second is force by calves muscles. One you exert instantly as soon as you stand on the scale "gravity force" the other you exert by calf muscles when you lift your body. Both forces are on the same direction so you add them. So does really my calf muscles exert 60+1.5 kgf? If so then you first stand on the scale exerting 60 kgf on the scale " your weight" then this force does not disappear a new force 60+1.5 kgf is exerted by calves muscles in the same direction that is a total of 60+60+1.5 kgf. So do really the calves muscles exert 60+1.5 kgf?

 

[origin]

So do really the calves muscles exert 60+1.5 kgf?

Yes.
I'm afraid it is hopeless, you are unable to grasp these basic physics concepts or you are trolling. The concepts have been explained to you by several people in several different ways and you just cannot or will not understand.
Apparently pretending you have 'discovered' something is more important than truly learning science which seems sad to me, but if living in your fantasy is more important to you then so be it.

 

[Michael 345]

the other you exert by calf muscles when you lift your body.

Ummmm so you are saying your calf muscles are pushing down on the scales and this downward force should be added to the gravity force pulling your body downwards?

Would that be correct?

If so it appears YOU are counting the calf muscles force TWICE
Once - to lift the body up
Again - to push the scales down

Any thoughts?

 

[James R]

They are not the same forces. One is gravity force by your body mass, the second is force by calves muscles.

Note that the only relevant force pushing down on the scales is the contact force between the person's feet and the top of the scales.

When the person is at rest on the scales, the scales push up on him with a force equivalent to 60 kg. By Newton's third law of motion, the person pushes down on the scales with a force of the same magnitude, and this is what the scales registers.

Where does gravity come into this? Gravity is a force the Earth as a whole exerts on the person on the scales. That is, the Earth pulls the person down with a force of 60 kg. By Newton's 3rd law, the person also pulls the entire Earth up gravitationally with a force of 60 kg. As I previously mentioned, the person does not fall to the centre of the Earth because the scales and the ground are both in the way. The result of the scales being in the way is that the scales must provide an upwards force on the person's feet of 60 kg, so that the person's overall acceleration is zero (Newton's 2nd law).

Now, if the person on the scales exerts (for a short time) an additional downwards force on the scales of 1.5 kg, then the scales will push up on them with an equal additional 1.5 kg. The total downwards force on the scales will then be 60 + 1.5 kg, and the equal upwards force on the person's feet will be 60 + 1.5 kg. Then, considering the forces acting on the person only, there will be an upwards force on the person due to the scales of 60 + 1.5 kg, and a downwards force on the person from the Earth's gravity of 60 kg. The net force on the person is then (60 + 1.5) - 60 = 1.5 kg upwards. By Newton's 2nd law, the person will then accelerate upwards.

Where do the calf muscles come into this? Notice that the calf muscles do not contact the scales, so they cannot exert any force on the scales. Rather, the force they exert is on bones in the person's leg. By a complicated series of action-reaction force pairs, the 1.5 kg force provided by the calf muscles is eventually transferred to a downward contact force on the scales of 1.5 kg and an equal and opposite 1.5 kg force on the person as a whole (Newton's 3rd law of motion, again).

Please tell me if you do not understand this. Ask questions if you need to. This is basic 17th century physics. We've understood this stuff for more than 4 centuries now, so it looks like the problem is most likely at your end.

 

[DaveC426913]

it looks like the problem is most likely at your end.

SciFo needs a Quotable Quotes thread for easy access.

 

[Yahya A.Sharif]

Now, if the person on the scales exerts (for a short time) an additional downwards force on the scales of 1.5 kg, then the scales will push up on them with an equal additional 1.5 kg. The total downwards force on the scales will then be 60 + 1.5 kg, and the equal upwards force on the person's feet will be 60 + 1.5 kg. Then, considering the forces acting on the person only, there will be an upwards force on the person due to the scales of 60 + 1.5 kg, and a downwards force on the person from the Earth's gravity of 60 kg. The net force on the person is then (60 + 1.5) - 60 = 1.5 kg upwards. By Newton's 2nd law, the person will then accelerate upwards.

So the muscles exerts only 1.5 kgf, the rest is 60 kgf which is the normal force due to gravity weight 60 kgf? a total downward force of 60+1.5 kgf? My question is still: If I exert a 1.5 kgf by calves muscle to a distance of 0.05 m " elapsed by the heels " then I do work of 1.5*9.8*0.05 Joules far smaller than the work I get when my heels return down to the ground. The heels do potential work of 60*9.8*0.05 Joules. However the work done by the calves muscles is only 1.5*9.8*0.05 Joules.

This is basic 17th century physics. We've understood this stuff for more than 4 centuries now, so it looks like the problem is most likely at your end.

It is not a problem at all to rethink of it, specially if scientists do not know what life exactly is.

 

[DaveC426913]

It is not a problem at all to rethink of it, specially if scientists do not know what life exactly is.

What makes you think that?

 

[cluelusshusbund]

This theory consists of three parts:

It is not a problem at all to rethink of it, specially if scientists do not know what life exactly is.

Woud you'r 3 part theory lead to the same conclusion if it was a 2 legged robot instead of a human who performed the experiment on the scales.???

 

[origin]

So the muscles exerts only 1.5 kgf, the rest is 60 kgf which is the normal force due to gravity weight 60 kgf? a total downward force of 60+1.5 kgf? My question is still: If I exert a 1.5 kgf by calves muscle to a distance of 0.05 m " elapsed by the heels " then I do work of 1.5*9.8*0.05 Joules

It is too bad that you have decided to argue in bad faith. You have been give clear explanations where you are wrong in your assumptions. Instead of exploring these issues you ignore them and then repeat the same false claims. Why are you doing that?

Why do you make the claim, "So the muscles exerts only 1.5 kgf"? This is clearly wrong; for you to move up your calf muscles must be exerting 60 + 1.5 kgf. Lets go over this yet again... When you stand on a scale with your heels raised about 5 mm off the scale, the scale reads 60 kgf. There is 60 kgf of gravity pushing down and and your calf muscles are exerting 60 kgf pushing up for a net force of 0 kgf. That is why you are not moving relative to the scale - there is no net force. When you are moving upwards (by raising up on your toes) there is the constant force of 60 kgf downward from gravity and your calf muscles are pushing your body upwards with 61.5 kgf (in this case). So there is a net upwards force of 1.5 kgf and therefore you move up. That's it, no magic, nothing surprising, just simple basic mechanics.

If you have a problem with that analysis please discuss it, don't just disappear for a few days and then return to repeat the same stupid claim!

 

[Yahya A.Sharif]

It is too bad that you have decided to argue in bad faith. You have been give clear explanations where you are wrong in your assumptions. Instead of exploring these issues you ignore them and then repeat the same false claims. Why are you doing that?

Why do you make the claim, "So the muscles exerts only 1.5 kgf"? This is clearly wrong;

No. This is not only my claim this the logical thing which James R said and I asked him about it. If your calves muscles exert 60+1.5 kgf then the scale should read your weight 60 kgf plus the force you exert on the scale 61.5 kgf or it should read 60+61.5 kgf but this does not happen. I ask you a question: The scale measures the forces, right? If it measures my weight 60 kgf before I lift my body, why it does not measure the force by calves muscles 61.5 kgf? If you are lying on the ground and you press a scale fixed on the wall the same way you lift your body, the scale will measure the force you move by against the ground friction this is what scales do they measure the forces whether you are lying on the ground or you are standing they measure the force by which you press to lift your body or the force you press to move against the ground's friction. The scale measures how much I press with my feet to lift my body and at the same time it measures the weight. Where did the weight disappear? Any force by my calves muscles must appear in the scale plus my weight which is always there " I am still standing on the scale" a total of 60+61.5 kgf.

Lets go over this yet again... When you stand on a scale with your heels raised about 5 mm off the scale, the scale reads 60 kgf. There is 60 kgf of gravity pushing down and and your calf muscles are exerting 60 kgf pushing up for a net force of 0 kgf

This is irrelevant. If you are standing on your feet balls" but at stationary" the weight measured by the scale is just 60 kgf. If we want to measure the force that the human lifts his body with we must start from the time the human is standing at stationary.
When the human is standing at stationary there are two forces on the scale: the weight of the human and the normal force by the scale which are equal, 60 kgf, the scale does not measure the net force, it measures the force by which it is pushed 60 kgf, if you push the scale with your calves muscles by 61.5 kgf it should measure the amount of push on it. As I said scales measure the push force if you are lying on the ground you are pushing a scale fixed to a wall to move and overcome ground friction it will measure the amount of push. This simple. If you are standing on a scale and lift your body by calves muscles it should measure the amount of force you push the scale with or the force by calves muscles 61.5 kgf. So the scale as you say should measure at least 61.5 kgf. So I do not think that you argue about the existence of the weight force. If the weight exists why the scale does not measure it ? we first agree that any push on the scale will appear because that what scales do they measure the push as above so they measure your force 61.5 kgf by calves muscles and also the human is still standing and touching on the scale so the scale should also measure his weight 60 kgf. A total of: the weight+the force by calves muscles=61.5+60=121.5 kgf the scale does not measure 121.5 kgf when the human lifts his body. I think James R and me agree that the calves muscles provide with 1.5 kgf which is logical, it is the weight 60 kgf plus the force of calves muscles 1.5 kgf that what the scale shows 61.5 kgf force.
And yes if you are going to lift your body the force by calves muscles is supposed to be greater than the weight because you need to create a non-zero net force upwards against the weight 60 kgf , F-60=non-zero then F is always greater than 60 kgf. But the experiment shows that the human exerts less than 60 kgf or 1.5 kgf , because the human does not lift 60 kgf he lifts a smaller than 60 kgf relative weight and again according to experiments the human of 60 kgf lying on belly on a concrete block does not damage his belly however a 15 kgf concrete block on the belly will damage it. Even though the mass of the human is four times the mass of the block. As in the first experiment the human lifts a relative weight less than 60 kgf in the second experiment the human belly bears this smaller than 60 kgf relative weight that why it does not damage. The spine cartilage bears a massive mass of the trunk,the arms and the head of approximately 50 kgf for years it cannot bear fifth of this mass as a rock even for days.