# How is mass divided by volume to measure density ?

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It says on google search

The Density Calculator uses the formula p=m/V, or density (p) is equal to mass (m) divided by volume (V). The calculator can use any two of the values to calculate the third. Density is defined as mass per unit volume.

However , it doesn't explain the force involved that divides mass by volume .

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17 minutes ago, Complexity said:

However , it doesn't explain the force involved that divides mass by volume .

Density is a measurement that compares the amount of matter an object has to its volume. The formula for density given in the reference is a mathematics formula. Hence "divided" means "division, as defined in mathematics"*. Divided does not imply a force splitting some amount of matter into smaller pieces. Does that answer your question?

Edited by Ghideon
Added first sentence, Density is a measurement that compares the amount of matter an object has to its volume.

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12 minutes ago, Ghideon said:

The formula for density given in the reference is a mathematics formula. Hence "divided" means "division, as defined in mathematics"*. Divided does not imply a force splitting some amount of matter into smaller pieces. Does that answer your question?

I' m afraid it does not answer my question !

Divide in math is also a separation process and has physical realities that accompany the math .

I'll extend my question to help save confusion .

What divides the mass of water (oceans) , around the earth ?

Edited by Complexity

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Playing games with definitions now ?
You are using 'divide' instead of 'separate'.
Division is well defined in math ( and Physics/Chemistry ), and the definition of density satisfies dimensional analysis.

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22 minutes ago, Complexity said:

Divide in math is also a separation process and has physical realities that accompany the math .

No, it does not. There are no physical realities that accompany the math.

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24 minutes ago, Complexity said:

I' m afraid it does not answer my question !

Ok! Then lets try again.

24 minutes ago, Complexity said:

Divide in math is also a separation process and has physical realities that accompany the math .

I'll extend my question to help save confusion .

What divides the mass of water (oceans) , around the earth ?

Ok, that has nothing to do with density as far as I can see. The volume of water and its mass and hence its density does not change when water is distributed in various locations around earth.

Stationary running water on earth (lakes, oceans puddles) is AFAIK held in place by gravity. Same goes for any liquid or fluid on any celestial body.

But the question is kind of complex if you want to consider other effects:
Earth rotation.
Tidal effects.
Heat and cold, creating currents, rain, and running water.
Water in the form of ice and snow

But this was posted in Theoretical physics, so I guess this is not about earth science?

Edited by Ghideon
added fluid and topic note

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22 minutes ago, Complexity said:

Divide in math is also a separation process and has physical realities that accompany the math .

It is not a "separation process" and there are no physical realities that accompany the math.

23 minutes ago, Complexity said:

What divides the mass of water (oceans) , around the earth ?

That has nothing to do with density or mathematics.

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4 minutes ago, swansont said:

No, it does not. There are no physical realities that accompany the math.

Let me get this straight ! You are saying that if we take the equation 1/2=0.5   , there is no physical realities that go with that equation ?

Wouldn't that make the equation meaningless ?

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Yes, without units attached to those numbers, that is an 'abstract' equation.

That is the beauty of Mathematics.
That abstract equation can be applied to all sorts of things ( units ), and give consistent results.
Even things that cannot be separated.

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1 minute ago, MigL said:

Yes, without units attached to those numbers, that is an 'abstract' equation.

Indeed , those numbers have to represent something ! You say units , do you mean joules for example ? Would a cake and 5 people be units ?

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8 minutes ago, Complexity said:

Let me get this straight ! You are saying that if we take the equation 1/2=0.5   , there is no physical realities that go with that equation ?

Wouldn't that make the equation meaningless ?

It is not meaningless: it defines the relationship between numbers.

What physical realities do you think those numbers represent? Apples?

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Mass is physical property. Sum of masses of the all particles added together.

Volume is physical property. Space used by particles by themselves and space between them.

One can use weight to measure mass.

Then calculate or measure volume.

Divide them both to get average density.

If you have volume and know average density (e.g. from tables) you can calculate mass. It is often used tool.

If you have mass, and know molar mass, you can tell quantity of particles or molecules (in uniform substance like distilled water).

Is it not the basics that you should learn on physics and chemistry lessons?

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2 minutes ago, Strange said:

It is not meaningless: it defines the relationship between numbers.

What physical realities do you think those numbers represent? Apples?

Apples , pears !  Anything that is dividable . i.e physical realities .

Edited by Complexity

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Sure.

! cake / 5 persons = 1/5 cake/person

Notice the units and consistent dimensional analysis.

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3 minutes ago, Complexity said:

Indeed , those numbers have to represent something ! You say units , do you mean joules for example ? Would a cake and 5 people be units ?

They don't have to be anything. They can be just numbers. But we can also choose to say that they relate to something (eg. 1 cake divided by 2 people = half a cake per person; or 1 joule divided by 2 seconds = 0.5 watts).

An important point is that when you do assign units to the numbers, they have to match on both sides of the equality.

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9 minutes ago, Complexity said:

Let me get this straight ! You are saying that if we take the equation 1/2=0.5   , there is no physical realities that go with that equation ?

Wouldn't that make the equation meaningless ?

The potential realities are in the application, not in the equation itself. You don’t need to physically divide anything in half in order to do the math

5 minutes ago, Complexity said:

Indeed , those numbers have to represent something !

No, they really don’t

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Notice how there is no explanation of the force or knife needed to separate the cake into 5 pieces  .

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Just now, swansont said:

The potential realities are in the application, not in the equation itself. You don’t need to physically divide anything in half in order to do the math

I agree but nonetheless the equation does represent something physical !

Perhaps I have not defined my question specifically enough .

What physical reality divides light by an unspecified physical volume ?

7 minutes ago, MigL said:

Notice how there is no explanation of the force or knife needed to separate the cake into 5 pieces  .

Exactly !

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Just now, Complexity said:

I agree but nonetheless the equation does represent something physical !

Not necessarily. Only if you choose to apply it to something physical. Mathematics is defined as a completely abstract set of relations. Some of it turns out to be useful for describing the physical world. A lot of it is not.

2 minutes ago, Complexity said:

What physical reality divides light by an unspecified physical volume ?

I don't know what that means. Do you mean something like the relationship between lux and lumens?

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1 minute ago, Complexity said:

What physical reality divides light by an unspecified physical volume ?

This is pretty far from the question I tried to help you with initially. Have to ask: What is your background knowledge? What concepts of math and physics are you familiar with that could act as a common starting point? Do you have a reference to something you read about light that raised the question?

Your question needs more context to be answered. For instance, what is a "physical reality"?

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7 minutes ago, Strange said:

I don't know what that means. Do you mean something like the relationship between lux and lumens?

I mean something like , we lit a candle in a room , the light emitted is not as bright as the flame , what physically divides the light around the room ?

Edited by Complexity

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10 minutes ago, Complexity said:
16 minutes ago, MigL said:

Notice how there is no explanation of the force or knife needed to separate the cake into 5 pieces  .

Exactly !

NOt really.
One is the physical act of separation.
The other is a mathematical concept.

Do you really not see the difference ?

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1 hour ago, Complexity said:

It says on google search

However , it doesn't explain the force involved that divides mass by volume .

Was that the google search,  babies version?

This is surely your cue to introduce one of your favourite topics - limits.

Beacause most type of density (and there are many current density, probability density......... the list is long)

As to the 'division', no it is not division at all it is the ratio of one independent quantity to another, as one of them tends to zero.

Edited by studiot

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The light spreads out into the volume of the room, and become more diffuse.

I could give you the mathematical relationship, but I'm getting the impression that would be useless.

Edited by MigL

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2 minutes ago, MigL said:

NOt really.
One is the physical act of separation.
The other is a mathematical concept.

Do you really not see the difference ?

Is it not true that the mathematical concept always represents a  physical act of separation although the physical part may be in imagination rather than physical applying it ?

If not , please provide a demonstration of other use .

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