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Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Yahya A.Sharif on 25/12/2019 15:16:58

Title: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 25/12/2019 15:16:58
Here is my discovery :
I can lift my whole body " 60kg" with my feet , but I can't lift a 60kg mass with my whole body.
Explanation :
The muscles have the force that can be measured by a scale. But when the mass which is lifted is my body my muscles can lift me with force far less than my weight .It is obviously that it is  related to the construction of the body , that is muscles being part of the body it lift.
 Mathematically we could measure the ratio between the muscles force lifting  a  mass and the muscles force lifting the body .The body weight and the mass weight must be equal "measured by a scale.
Email: yahya-sharif3@hotmail.com
Yahya Awad Sharif
ُ


Title: Re: Can a mass be lifted with force less than its weight?
Post by: Origin on 25/12/2019 18:28:51
I can lift my whole body " 60kg" with my feet , but I can't lift a 60kg mass with my whole body.
Explanation:  you can't lift it because that would be a total 120 kg you would be trying to lift.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 25/12/2019 19:42:25
I can lift my whole body " 60kg" with my feet , but I can't lift a 60kg mass with my whole body.
  you can't lift it because that would be a total 120 kg you would be trying to lift.
Let it be sitting down on a chair  " no affect of body weight on  my feet  " and I put 20 kg above my feet, would that be easy to raise my feet ?  what would be easy ? to lift the 20kg or to lift a 60kg?
Title: Re: Can a mass be lifted with force less than its weight?
Post by: evan_au on 25/12/2019 20:46:33
Quote from:
Let it be sitting down on a chair
When you lift weights to a standing position, you engage your gluteus maximus (butt muscles), which are some of the largest muscles in the human body.

These can't help much when you are seated, so you can lift a reduced weight with your feet.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Origin on 25/12/2019 21:17:09
Go to the gym and use the leg press equipment and you will find that you can easily lift more than your body weight.  There is no magic going on here.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 25/12/2019 21:19:19
Quote from:
Let it be sitting down on a chair
When you lift weights to a standing position, you engage your gluteus maximus (butt muscles), which are some of the largest muscles in the human body.

These can't help much when you are seated, so you can lift a reduced weight with your feet.
I might be misunderstood in my previous post :
 lifting the body "60kg"is while standing, lifting the 20 kg is while sitting  , both I lift with my only feet muscles without using my leg muscles. I claim it would be far more easy to left the 60kg"my body" than to lift the 20kg, because a body can lift itself easier than it lift a mass.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: evan_au on 25/12/2019 21:46:23
Quote from: Yahya A.Sharif
I claim it would be far more easy to left the 60kg"my body" than to lift the 20kg, because a body can lift itself easier than it lift a mass.
Your body does have mass, so you have to include that in what the body is lifting.

We are so used to holding up the body's mass while standing or walking, that it seems "effortless".
- Now try walking up 10 floors of a building via the stairs - you are lifting your body mass against gravity, and that takes energy.

On Earth's surface, we can often ignore the difference between weight and mass, because a stationary mass of 1kg exerts a force of 1kg-Force =9.8 Newtons.
- One place where these are very different is in the "vomit comet": planes used for astronaut training by NASA, ESA and the Russian space agency (and able to be hired for joy rides, too).
- During the microgravity part of the flight, you could (slowly) lift a ton of mass - because it is weightless.
- But you need to get out of the way quickly, because after 30 seconds, the plane bottoms out, and the weight increases to 2 tons, which would crush you (and damage the plane).
- In this phase of the flight, your weight increases to twice normal, which most people can withstand by standing while holding onto a handrail. But they require that you don't try to walk in this situation, as you are likely to fall and break bones. (The safety staff on the flight are trained to walk under these G-Forces - but they do so slowly and carefully!)
- Under 2g acceleration, I expect that you would struggle to lift yourself alone, with no weights.
See: https://en.wikipedia.org/wiki/Reduced-gravity_aircraft
https://omegataupodcast.net/330-parabolic-flights-at-airzerog/
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 25/12/2019 22:14:37
Quote from: Yahya A.Sharif
I claim it would be far more easy to left the 60kg"my body" than to lift the 20kg, because a body can lift itself easier than it lift a mass.
Your body does have mass, so you have to include that in what the body is lifting.
It doesn't matter its weight or mass , the scale will measure its true mass and weight, but the muscles uses less force than the body weight to lift it through the experiments I mentioned.
- Now try walking up 10 floors of a building via the stairs - you are lifting your body mass against gravity, and that takes energy.
You didn't compared it with walking up carrying a load.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: alancalverd on 26/12/2019 09:48:26
Your legs account for about 1/3 of your mass, so the muscles in your legs are only lifting 40 kg, and they are, as pointed out, huge.

The argument above is considerably confused but it seems to revolve around either "deadlifting" another 60 kg to the mass your legs are lifting, which is manageable with training but not what we evolved to do, or "curling" 20 kg from a seated position, using the puny muscles in your skinny arms - again manageable with training, but easier if you are some other kind of ape. Adult humans differ from other primates in  being obligate bipeds, with long rear limbs and very little capacity for brachiation (though babies can grasp and hang long before they can walk), which is why we are reluctant to swing through the trees and sleep in a nest.   

The trick of a good backpack is that the frame transfers the load to your hips. I often wear a "lead apron" for radiation protection at work: the best modern design uses a skirt and jacket to distribute the weight better than a simple tabard.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 26/12/2019 12:11:18
Your legs account for about 1/3 of your mass, so the muscles in your legs are only lifting 40 kg, and they are, as pointed out, huge.
It is absolutely easy to raise legs up while sitting , and it is absolutely  hard to raise legs up in a case 20 kgs is tied to them, calculating  the doubled weight " 20kg the weight of my legs and the mass 20 kg " won't give the normal results  , the difference will be huge.

Title: Re: Can a mass be lifted with force less than its weight?
Post by: alancalverd on 27/12/2019 12:18:19
Definition of weight: force required to lift a mass. If you get the physics right, it will be easier to discuss the physiology.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 27/12/2019 17:32:30
 lifting the body "60kg"is while standing, lifting the 20 kg is while sitting  , both I lift with my only feet muscles without using my leg muscles. I claim it would be far more easy to left the 60kg"my body" than to lift the 20kg, because a body can lift itself easier than it lift a mass.

The distribution of mass is different and the muscle groups engaged are also different. Have you heard of the concept of leverage? https://en.wikipedia.org/wiki/Lever#Force_and_levers If you consider your legs to be levers and the load is placed at your feet, then that is the worst possible place to put the weight in terms of lifting difficulty. If you put the load on your knees or thighs, it would be easier to lift despite having exactly the same mass.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 31/12/2019 05:25:31
Have you heard of the concept of leverage? https://en.wikipedia.org/wiki/Lever#Force_and_levers
Yes I have.
If you consider your legs to be levers and the load is placed at your feet, then that is the worst possible place to put
the weight in terms of lifting difficulty.
That doesn't  have significant effect
If you put the load on your knees or thighs, it would be easier to lift despite having exactly the same mass.
I don't think putting a 60 kg load on my thighs is a good idea.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: evan_au on 31/12/2019 05:57:17
Quote from: OP
My great new discovery : A mass can be lifted with force less than its weight
This is not a new discovery.

This was achieved by an invention known since antiquity: The "Block and Tackle":
https://en.wikipedia.org/wiki/Pulley#Block_and_tackle

(Kryptid also mentions levers, above, which achieve the same force-multiplying effect by a different mechanism...)
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 31/12/2019 06:01:51
That doesn't  have significant effect

It has a very significant effect:
Double the length of the lever, and you double the force produced. So placing a 20 kilogram weight on your knees would require you to exert only about half as much force as you would need to lift that same weight if it was at your feet.

I don't think putting a 60 kg load on my thighs is a good idea.

Like I said before, the distribution of mass and the muscle groups employed are different in that scenario than they are for when you stand up from a sitting position.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Bored chemist on 31/12/2019 12:03:41
both I lift with my only feet muscles
Feet have very little muscle.
So, it's clear that, as usual, you don't know what you are talking about.

Why do you do this?
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 02/01/2020 18:08:08
The distribution of mass is different and the muscle groups engaged are also different. Have you heard of the concept of leverage? https://en.wikipedia.org/wiki/Lever#Force_and_levers If you consider your legs to be levers and the load is placed at your feet, then that is the worst possible place to put the weight in terms of lifting difficulty. If you put the load on your knees or thighs, it would be easier to lift despite having exactly the same mass.
I can lift my 60 kg body with only my weak feet muscles when trying to pick a fruit on a tree.

Let's for the example above  the foot is 30 cm or 0.3 meters, Now let's calculate for a 0.3 lever:
First the lever will be class 3 :
The weight for 60 kg will be 60*9.8=588 Newtons.
The force of my feet  is distributed along the feet  , from both  toes to both  heel .Letís  the muscles force  is  focused on the heel which is the maximum force of muscles could be.
Class 3  is the fulcrum at the toes  , and in this case both the weight of my body and the force of my feet will be exactly at the heel:
F: force of my weight
f: force of  muscles strength
L: the distance  of the weight from the heel to the toes.
l: distance of the muscles force from the heel to the toes.
f * l=FL
F=588   and L=l =0.3

f*0.3=588*0.3
f=588  Newton
The muscles force to lift 60 kg according to current physics and the lever idea must be  588 Newtons
The muscles force  actually is far less than 588 Newton but it  lift the body .
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Bored chemist on 02/01/2020 20:08:01
I can lift my 60 kg body with only my weak feet muscles when trying to pick a fruit on a tree.
Actually, it is mainly your calf muscles doing that, and they are (obviously) rather strong.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Bored chemist on 02/01/2020 20:15:38
What you seem to have noticed- it isn't news to science- is that a thing can  produce a force that is greater than its own weight.
So what?
A hammer does that.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: jeffreyH on 02/01/2020 20:37:11
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 02/01/2020 21:59:33
I can lift my 60 kg body with only my weak feet muscles when trying to pick a fruit on a tree.

You must have forgotten about the significant muscle mass in your legs.

The muscles force  actually is far less than 588 Newton but it  lift the body .

What was it about, "the distribution of mass and the muscle groups employed are different in that scenario than they are for when you stand up from a sitting position" that you didn't understand?
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 02/01/2020 22:59:05
A thing could be noticed is the inertia of one's body  seems far less than actual body mass inertia, so walking is easy  , in fact all movements of a body are effortless , moving any part of the body is easy compared to the body mass, a person feels like his body is lighter than mass of the body.
Is it possible for person to carry 70 kg rock and run ? I don't think an an average person who is not bodybuilding will even be able to lift a 70 kg weight .So how we even carry our bodies?
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 02/01/2020 23:05:23
A thing could be noticed is the inertia of one's body  seems far less than actual body mass inertia, so walking is easy  , in fact all movements of a body are effortless , moving any part of the body is easy compared to the body mass, a person feels like his body is lighter than mass of the body.

What something "seems" like or "feels" like is not the same as what it actually is. Our muscles are collectively more than strong enough to move our bodies. An average man can leg press more than his own weight. That doesn't even take into consideration the other muscles, like those in your core and back, that help with standing up.

Is it possible for person to carry 70 kg rock and run ? I don't think an an average person who is not bodybuilding will even be able to lift a 70 kg weight .So how we even carry our bodies?

Are you serious? Your body has weight. If you are not carrying the rock, you are only carrying your own body's weight. When you carry a rock, you are carrying both your body's weight and the weight of the rock. Carrying a rock is obviously harder because the total weight being carried is higher. That should be obvious.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 02/01/2020 23:25:02

An average man can leg press more than his own weight. That doesn't even take into consideration the other muscles, like those in your core and back, that help with standing up.
I'm not talking about legs I'm talking about feet which is used to carry up a person as I mentioned  , The force which should   lift a person by his feet is 588 Newton , do you think the feet will provide such force when presses .?
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 02/01/2020 23:32:32
I'm talking about feet which is used to carry up a person

The muscles in your feet do not lift you own their own. Your leg muscles are involved.

The force which should   lift a person by his feet is 588 Newton

Your calculation for that wasn't even sensible. People don't stand up by using their feet like that.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 03/01/2020 05:56:33
The muscles in your feet do not lift you own their own. Your leg muscles are involved.
Right , the force involves my legs force , but do you think the force of feet and legs pressing equal 588 Newton ? or even close to it? you can just press your feet and find out how weak it is .
Your calculation for that wasn't even sensible. People don't stand up by using their feet like that.
I presented specific example , which turned out to be very sensible.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 03/01/2020 06:56:40
Right , the force involves my legs force , but do you think the force of feet and legs pressing equal 588 Newton ? or even close to it? you can just press your feet and find out how weak it is .

It doesn't need to because getting out of a chair isn't akin to the scenario you calculated.

I presented specific example , which turned out to be very sensible.

No it wasn't. You stated in your calculation that you put the fulcrum at the feet. If I'm sitting in a chair and trying to get into a standing position, the fulcrum would be at the knee instead. Or at least one of the fulcrums would be. Standing up uses many joints and many points of force application. A calculation assuming a simple lever breaks down because of that. You would need to calculate the forces acting along all of the relevant points of the body.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 03/01/2020 07:30:26
It doesn't need to because getting out of a chair isn't akin to the scenario you calculated.
If I'm sitting in a chair and trying to get into a standing position, the fulcrum would be at the knee instead. Or at least one of the fulcrums would be. Standing up uses many joints and many points of force application. A calculation assuming a simple lever breaks down because of that. You would need to calculate the forces acting along all of the relevant points of the body.
Actually , the example doesn't involve body sitting or standing. Reply #16
You stated in your calculation that you put the fulcrum at the feet
The calculation is considering the fulcrum to be at the toes
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Origin on 03/01/2020 13:57:03
The OP asked:
Can a mass be lifted with force less than its weight?

The obvious answer is:
Of course not.  It is embarrassing that someone would even ask the question.

He cannot be convinced he is wrong, he has shown that he Is impervious to logic.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Bored chemist on 03/01/2020 17:02:11
It seems to me that he hasn't understood the issues.
 Yahya A.Sharif
I can use a brick and a plank of wood as a fulcrum and a lever.
With those I can lift your weight very easily.



But the force at the "short" end of the lever- where it lifts your weight is still equal to your weight. (and eh force on trh brick is a bit more than your weight.

That's elementary physics.

You seem to think it is some sort of "magic".
It's not.

If you use your "feet" to lift yourself (actually, you use your calf muscles)
https://en.wikipedia.org/wiki/Calf_(leg)
 then the fulcrum is your toes. The load is your weight pressing down on your ankles and the force is applied from the calf muscles, via the achilles tendon.
https://en.wikipedia.org/wiki/Achilles_tendon

The load in that tendon is several times MORE than your weight.
Your calf muscles can each supply a force of several times your body weight.

They are remarkably strong, but it still isn't a breach of physics.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Kryptid on 03/01/2020 17:33:23
Actually , the example doesn't involve body sitting or standing. Reply #16

Oh, I see now. 30 centimeters seems an unreasonable distance for the lever of your foot. Even if your foot was that long, you don't stand on your actual toes when you stretch upwards. You are standing on the ball of your foot instead. Also, your center of gravity wouldn't be right at your heel. It should be closer to the center of your foot for the sake of balance.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: yor_on on 07/01/2020 16:29:29
I don't think so?
The inertia needs to be overcome, even if the weight differ from the Moon to the Earth.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Petrochemicals on 08/01/2020 10:55:46
Yes weight can be lifted with a force less than it, through mechanical advantage, it is however possible to put less energy in than an object would gain.

https://en.m.wikipedia.org/wiki/Torque
Title: Re: Can a mass be lifted with force less than its weight?
Post by: yor_on on 08/01/2020 21:02:01
Yes, that's true PC, but the energy spent by lifting it should be the same as if was someone stronger f.ex, using a winch as in pulleys. If there was a way to spend less energy I would be very surprised. To me it seems as if you have a mass you will find a inertia, the inertia won't change even though the weight might. That's how I see it.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Yahya A.Sharif on 11/01/2020 09:06:59
will a person climbing a ladder and falling on a generator turbine generate energy from nothing?
The input biological body energy exerted will be equal to the output energy represented by the body weight on the turbine ,and that  regardless of the calculations of muscles force and body weight .So energy is conserved
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Bored chemist on 11/01/2020 12:30:02
will a person climbing a ladder and falling on a generator turbine generate energy from nothing?
No.
They will generate energy from food (which got it from sunlight).
But nobody said  this wasn't the case, so why did you ask the question?

Quite a lot of the energy in the food is "wasted" as heat, but that's another matter.
Overall, energy is conserved.
Title: Re: Can a mass be lifted with force less than its weight?
Post by: Origin on 13/01/2020 14:11:07
Why do our bodies  break fundamental laws of physics that is the laws regarding this thread?
They don't, this has been pointed out to you many times in this thread.
Does that mean the body have its own physics that governed by different laws and explains different phenomena of the body and  theses laws connected to each other in a way that the body has its own physics?
Of course not, don't be silly