Mass

[Burgerman]

Dont know what that means.
No taring involved. Van is on the street!
Your taring would be how to measure mass at 1g.
Or the "weight" if the earth had no air but we would be dead...

I do know that "weight" is a thing measured by a weighing device. And that the weight at 1G of EVERYTHING measured on earth is reduced by the atmosphere it floats in. Including its lead battery...
The thing that adds confusion here (on purpose by me) is that a minus weight (in air) of a helium balloon makes people scratch their heads.
As it does in fact have zero (minus in fact) weight when measured and a positive varifiable mass. HERE ON EARTH.

Weight = whatever the scale says it does.
Mass = whatever the mass measured by acceleration says it is.

And that both are different on earth.
And that the WEIGHT of a helium balloon is a negative figure on earth where we are weighing it.
The mass of this helium ballon is only equal to its measured INERTIAL MASS in a vacuum where it is a obviously positive figure and we are NOT in a vacuum...

In physics weight is not a fixed property. Its what it weight on a scale. Wherever you do it. On earth thats a less than one number as it is boyant in air.

On the moon, a 6KG Mass will weigh 1/6th of its weight on a measuring scale. If in fact the moon had zero atmosphere and was exactly 1/6th of earths gravity. And that weight is CORRECT acording to current physics. You are in error thinking that its some unchangable characteristic. It isnt. Only mass always remains the same - (at least at speeds nowhere near light.) Thats why we have weight AND mass measurements.

By removing all the efects that affect its measured weight you are just measuring its mass. That does not apply to the van. We dont live in a vacuum.

Remember that the van is on the street on earth. And we added helium balloons... The vans weight reduced more than its mass did.

[Burgerman]

In the beginning when philosophers etc and ignorance was common weight of an object was defined as its RESTING mass (no g forces etc) and nothing affecting its weight. So its mass and weight would be the same.

Once einstein came along this was then abandoned. Because there is no such thing in einsteins relativity as stationary so there isnt a way to decide if anything is at rest sinse every speed is simply relative.

Then mass became what you would measure through inertia, weight became operational or measured including that van...


Wiki:

The operational definition, as usually given, does not explicitly exclude the effects of buoyancy, which reduces the measured weight of an object when it is immersed in a fluid such as air or water. As a result, a floating balloon or an object floating in water might be said to have zero weight.

So MASS = inertia.
Weight = whatever the scale says. Even on mars.

[Burgerman]

Wiki again... https://en.wikipedia.org/wiki/Weight

In a different gravitational field, for example, on the surface of the Moon, an object can have a significantly different weight than on Earth. The gravity on the surface of the Moon is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity, and therefore its weight, is only one-sixth of what the object would have on Earth. So a man of mass 180 pounds weighs only about 30 pounds-force when visiting the Moon.

Note, the WEIGHT of the man is 30lb.
His mass is 180lb.

Gravity strength, acceleration, centrifugal effects, floation, electrostatic or electromagnetic affects are all things that change the expected mass to some other figure we call weight.

[Burgerman]

Heres another.
According to einstein, a charged battery is a couple of micrograms heavier than a discharged one.

[slomobile]

So MASS = inertia.
Weight = whatever the scale says. Even on mars.

Yes. Whatever the scale says, provided the scale has been properly prepared. If you skip preparation, what you get is the apparent weight.
On Mars, actual genuine weight differs from mass because you are in a different gravitational field. At sea level on Earth, weight of an object is equal to its mass. High in the mountains on earth weight is very slightly less than mass because you are further from the center of the earth. Apparent weight is also less at high altitudes because the air is less dense, thus less buoyant. Whether in air, or in a vacuum, or in Jello pudding, the actual weight of an object is the same if it experiences the same gravitational attraction.

The apparent weight can vary due to buoyancy. The force measured on a scale will be the force of gravity (m_obj * g) minus the force of buoyancy (m_disp * g) where m_disp is the mass of the surrounding fluid displaced by the object. If the buoyant force is much larger than the weight force, you need to tare the scale at the value for the expected buoyancy. Maybe I'm using "tare" incorrectly, I'm talking about the little dial that lets you set what reading the scale starts at with nothing on it. Set it to a positive value equal to calculated buoyancy, as the balloon pulls up on the scale, the value displayed will be reduced, but not negative. The scale will display the actual non-negative weight of the helium filled balloon. Alternatively, if you insist on the scale starting at 0 and not doing math, you can enclose the scale and everything you measure in a sealed box and suck out the air to eliminate the buoyancy. The helium balloon will stop floating in the absence of air and you can weigh it directly.

Re: Einstein and charged batteries being heavier https://chargerblog.com/do-batteries-ge ... n-charged/

[Burgerman]

Yes. Whatever the scale says, provided the scale has been properly prepared. If you skip preparation, what you get is the apparent weight.

appARENT WEIGHT or what the scale, weighbridge etc reads is the only "weight" that matters here. You will never see anyone taking a van or anything else down to Nasa's vacuum test facility to weigh it.
Even scientists refer to true mass as mass. And weight ON ANY PLANET or as weighted in a lab, as the weight. You can call it apparent weight if you want. But that IS its weight!

On Mars, actual genuine weight differs from mass because you are in a different gravitational field. At sea level on Earth, weight of an object is equal to its mass. High in the mountains on earth weight is very slightly less than mass because you are further from the center of the earth. Apparent weight is also less at high altitudes because the air is less dense, thus less buoyant. Whether in air, or in a vacuum, or in Jello pudding, the actual weight of an object is the same if it experiences the same gravitational attraction.

Obviously. Thats why we use MASS when we want an objects unchangable locked same anywhere figure. And weight when we want to know its "weight"!

The apparent weight can vary due to buoyancy. The force measured on a scale will be the force of gravity (m_obj * g) minus the force of buoyancy (m_disp * g) where m_disp is the mass of the surrounding fluid displaced by the object.

Obviously. But we do not weight stuff in a vacuum... And thats why we call it weight and not mass.

If the buoyant force is much larger than the weight force, you need to tare the scale at the value for the expected buoyancy.

No ecause that is not what it actually weighs... Thats its mass.

Maybe I'm using "tare" incorrectly, I'm talking about the little dial that lets you set what reading the scale starts at with nothing on it. Set it to a positive value equal to calculated buoyancy, as the balloon pulls up on the scale, the value displayed will be reduced, but not negative.

Again all obvious. You biased the scale so that you do not get its weight on earth where we live, and you measured its mass. We all KNOW that it has positive mass.
My argument was that the van mass was signifficantly greater than its weight once filled with helium balloons. Not weiighed "in a vacuum"...

The scale will display the actual non-negative weight of the helium filled balloon. Alternatively, if you insist on the scale starting at 0 and not doing math, you can enclose the scale and everything you measure in a sealed box and suck out the air to eliminate the buoyancy. The helium balloon will stop floating in the absence of air and you can weigh it directly.

You keep on stating the blindingly obvious.
But we dont weight vans in a box sealed in a vacuum do we...
We dont in fact weigh anything that way.
The reason that scientists talk about WEIGHT on different planets for example is because APPARENT WEIGHT is what matters. Same on earth. Not its mass as measured in a vacuum. Because we live on earth. And in the atmosphere. Because its weight is as important as its mass. But hugely different in different conditions. In space its mass is all that matters. Because thats how you calculate required thrust/acceleration.
On a planet when landing BOTH mass and weight matter.

If we did then thats not its weight on earth in the street outside my house is it.
The weight of balloon full of helium is quite obviously less than its inertial mass ON EARTH. And identical in a vacuum. But we dont live in a vacuum. Certainly not in my street!

[slomobile]

You can call it apparent weight if you want. But that IS its weight!

Most of the time, yes. The only time it makes a difference is when weighing something lighter than the same volume of buoyant environment. But then, the difference really does matter. Depending on what the end purpose is, you may want apparent weight if you want to know the tension in the string, or actual weight if you want to calculate how much that same item would weigh on a different planet.

But we do not weight stuff in a vacuum... And thats why we call it weight and not mass.

We weigh stuff in vacuum all the time in labs where fine precision is required. https://www.physics.purdue.edu/demos/di ... item=2A-08

If the buoyant force is much larger than the weight force, you need to tare the scale at the value for the expected buoyancy.

No ecause that is not what it actually weighs... Thats its mass.

No. It certainly is not its mass. As you said before, mass needs to be measured with inertial techniques. Or derived from weight and knowledge of the gravitational field where the weighing occurred.

My argument was that the van mass was signifficantly greater than its weight once filled with helium balloons. Not weiighed "in a vacuum"...

And I have always been saying that you are just plain wrong about that. Whether in a vacuum, in a tree, in a box with a fox, there is no such thing as negative weight. I challenge you to find any authoritative source that says there is.

The reason that scientists talk about WEIGHT on different planets for example is because APPARENT WEIGHT is what matters.

Ok, the apparent weight of a full gallon of water partially submerged in water is 1lb. What is its weight on Mars. Show your math.

The weight of balloon full of helium is quite obviously less than its inertial mass ON EARTH. And identical in a vacuum. But we dont live in a vacuum. Certainly not in my street!

That is neither obvious or true. If it were, you could cite a reputable source that agrees with you. Thus far every link you've shown has not said that.
https://en.wikipedia.org/wiki/Apparent_weight

[Burgerman]

I give up.

I dont need a source
I could WEIGH the van. Park it on a good weighbridge. Guess why its called a weighbridge. Then add the balloons. And its weight will reduce. So will its mass. But not by as much.

You can go on about in a lab and weiging stuff in a vacuum all you want. But thats not how we weigh stuff is it.
I weighed myself a month ago. I didnt do it in a vacuum did I?
Nor does anyone else.

The point about the van is that it IS ON MY STREET.
Obviously if I found some way to weigh that in a vacuum it would be slightly more. But thats not what I am weighing.

[LROBBINS]

Weight is a vector with magnitude and direction. Its magnitude is always positive, but its direction may be positive (toward the center of the earth or other dominant gravitational force) or negative (away from the center of the earth ...) in which case when doing the vector sum of the weight of various objects it will have a negative sign (which we can certainly call "negative weight" or "lift" or "buoyancy").

[Burgerman]

Correct.

So perfectly legit to say a helium balloon has a negative weight out in the street orinside the van. Because that is the situation we are actually measuring it in.

[slomobile]

Correct.

So perfectly legit to say a helium balloon has a negative weight out in the street orinside the van. Because that is the situation we are actually measuring it in.

No. You are simply wrong. You could be right if you said "perfectly legit to say a helium balloon has a negative apparent weight. The apparent weight can be negative because it includes the effects of buoyancy. The actual weight is never negative. The actual weight vector is always directed toward the prevailing mass. If it is not, you know that something other than gravity is acting on the object being weighed, thus apparent weight. Balloons have positive weight. Helium has positive weight. There is no way to add JUST those two positive weights to get a negative weight. If you insist that there is, I insist on a source.

[Burgerman]

When anyone weighs anyting ever on earth, they dont say aparent weight.

When I buy anything in a shop by weight. When I drive a van onto a weighbridge. When I look on the packaging of anything I buy, it says weight. And this weiht is what you see when you weigh it. Nobody ever says the apparent weight is x.

Obviously everything has some floatation, even that supermodel that just lost another 2lb. She and nobody in the history of the world says she lost an aparent 2lb... My weighing scales dont say apparent weight either. And you know this perfectly well. So when you say I cant say it has negative weight, I can. And have. Its no different to what the whole planet do with everything that is weighed.

Nobody weighs anything in a vaccuum, or calls things they weigh "apparent" weight... Tha includes weighing scales and weighbridges. And weights...

Even precision scientific weights for science labs call weight, weight! Heres a cheap set of calibration weights. Not even here are these called apparent weight...
https://www.amazon.co.uk/HFS-Scale-Bala ... r=1-6&th=1