How much does the Earth weigh?

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BenTheH33

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How much does the Earth weigh?
« on: 23/11/2010 10:30:04 »
BenTheH33 asked the Naked Scientists:
   
One thing I have wondered is how much does earth weigh? How many pounds does earth way, and if we don't yet know, do you think it would ever be possible to guess accurately?

KEEP UP THE GREAT WORK!!!

Ben

What do you think?
« Last Edit: 23/11/2010 10:30:04 by _system »

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Offline Pikaia

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Offline QuantumClue

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How much does the Earth weigh?
« Reply #2 on: 23/11/2010 12:22:49 »
The earth weighs 6.5 x 10^27 in tons. But this is nothing on astronomical terms. Even a spoonful of neutron star would weigh about the same as all the buildings on earth.

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david holthaus

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How much does the Earth weigh?
« Reply #3 on: 23/11/2010 13:30:05 »
david holthaus asked the Naked Scientists:
   
how much does the earth weigh?

What do you think?
« Last Edit: 23/11/2010 13:30:05 by _system »

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Offline Bill S

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How much does the Earth weigh?
« Reply #4 on: 23/11/2010 14:58:28 »
Calculating the mass of the Earth is fairly straightforward, but weight is relevant only in relation to gravity, but perhaps it was mass you were thinking of, in which case it's something like 5.9737 × 10ˆ24kg.
There never was nothing.

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Offline maffsolo

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« Reply #5 on: 23/11/2010 15:06:49 »
I found a site that relates to the mass of the earth...
http://hypertextbook.com/facts/2002/SamanthaDong2.shtml
Bill S has it I found this may be an approximate derived calculation since there is mass collecting here from space, constantly.

Let's see if I have it correct
Below: In this definition of Weight I will say earths weight is zero. If this is a true definition...

Weight is the force that results from the acceleration by gravity on the mass of an object.[1]

Sometimes it is defined in operational terms of the weighing process as the force exerted by an object on its support,[2] which also illustrates the condition of weightlessness.

Standing at rest on a weighing scale on Earth, a person's weight equals its mass multiplied by the gravitational acceleration of Earth. However, in a free falling elevator, a scale indicates a zero weight, as no net force is exerted by the body on the support; the person experiences weightlessness. Similarly, in a space craft in orbit around the Earth the weight is also zero, as the orbit represents a free fall. On the surface of the Moon, an object's weight is approximately one sixth of the weight at rest on Earth, as the gravitational force exerted by the Moon is much smaller than that of Earth.

The weight of an object, often denoted W, is defined as the gravitational force exerted on it. It is the product of the mass m of the object and the local gravitational acceleration g:[3] W = m g. In the International System of Units (SI), the unit of measurement for weight is that of force, the newton.

On the surface of the Earth, the acceleration due to gravity is approximately constant; this means that the magnitude of an object's weight on the surface of the Earth is proportional to its mass. In situations other than that of a constant position on the Earth, so long as the acceleration does not change, the force it exerts against support in any accelerated frame is proportional to its mass, also. In everyday practical use, therefore, including commercial use, the term weight is commonly used to mean mass.

http://en.wikipedia.org/wiki/Weight
« Last Edit: 23/11/2010 15:14:37 by maffsolo »

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Offline syhprum

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How much does the Earth weigh?
« Reply #6 on: 23/11/2010 16:30:34 »
The value quoted by QuantumClue is not correct the correct value is 5.9742 × 10^24 kilograms
« Last Edit: 23/11/2010 16:32:40 by syhprum »
syhprum

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Offline Bill S

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« Reply #7 on: 23/11/2010 16:55:25 »
We are talking about mass rather that weight, yes?

We seem to have two threads dealing with the same question. [:P]
« Last Edit: 23/11/2010 17:10:43 by Bill S »
There never was nothing.

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Offline Bill S

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« Reply #8 on: 23/11/2010 17:08:55 »
Good answer, maffsolo, but,David, is that what you were looking for?
There never was nothing.

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Offline maffsolo

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« Reply #9 on: 23/11/2010 17:18:31 »
We are talking about mass rather that weight, yes?

We seem to have two threads dealing with the same question. [:P]

http://www.thenakedscientists.com/forum/index.php?topic=35366.msg331835#msg331835

There seems to be a controversy on terminology with this question We need to call a doctor in to prescribe a solution
Yelling for MEDIC @#$%^&

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Offline BenV

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How much does the Earth weigh?
« Reply #10 on: 23/11/2010 17:22:13 »
Two identical questions merged - sorry if it's a bit muddled right now!

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Offline maffsolo

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« Reply #11 on: 23/11/2010 17:25:59 »
Two identical questions merged - sorry if it's a bit muddled right now!

Thank you for the first aid

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Offline QuantumClue

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How much does the Earth weigh?
« Reply #12 on: 23/11/2010 17:35:34 »
The value quoted by QuantumClue is not correct the correct value is 5.9742 × 10^24 kilograms

Mine was in tons. Not kilograms.

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Offline imatfaal

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« Reply #13 on: 23/11/2010 17:54:55 »
10^27 tonnes DOES NOT equal 10^24 kilogrammes.  Your answer was 10^6 times too big
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

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Offline QuantumClue

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How much does the Earth weigh?
« Reply #14 on: 23/11/2010 18:08:49 »
Oh I see. Well that's not good.

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Offline maffsolo

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« Reply #15 on: 23/11/2010 19:04:22 »
Plug and chug convergence calculator

http://www.onlineconversion.com/weight_all.htm




5.9736e+24 kilogram = 9.4068097813e+23 stone

And I thought Earthy was the third stone from the Sun
« Last Edit: 23/11/2010 19:09:13 by maffsolo »

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Offline QuantumClue

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« Reply #16 on: 23/11/2010 19:37:41 »
Plug and chug convergence calculator

http://www.onlineconversion.com/weight_all.htm




5.9736e+24 kilogram = 9.4068097813e+23 stone

And I thought Earthy was the third stone from the Sun

I apologize, we all make mistakes. That calculator will definately come in useful in the future.

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Offline maffsolo

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How much does the Earth weigh?
« Reply #17 on: 23/11/2010 19:51:18 »
Plug and chug convergence calculator

http://www.onlineconversion.com/weight_all.htm




5.9736e+24 kilogram = 9.4068097813e+23 stone

And I thought Earthy was the third stone from the Sun

I apologize, we all make mistakes. That calculator will definately come in useful in the future.

No need to appologize I am the master of mistakes.
I can do best with my eyes closed.

I sat here and tried to convert it and I found I was slipping, to double check myself I went to see if my conversion was correct. I was having a bit of a problem with a simple setup and combinding the exponents for a result.

I am here just to keep my gray matter in one mass, I can be trained...:)

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Offline Foolosophy

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How much does the Earth weigh?
« Reply #18 on: 30/11/2010 13:07:57 »
The weight of the earth is equal to zero because it is in free fall motion around the sun

The earth's MASS however can be determined in a variety of ways

cheers

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Offline thedoc

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« Reply #19 on: 10/12/2010 15:26:06 »
We discussed this question on our  show
  Chris -  The stated weight – mass, we should more accurately, of the Earth is about 6 x 1024 kilograms. In other words, if you turn that into tons, it’s 6 with 21 zeros after it, tons. So pretty heavy, but the big question is and this is where Dave can help me out, how do we actually know that something on the scale of the Earth that we can't physically put on a pair of scales, how do we know how much that weighs because Archimedes famously said, “If you give me a lever long enough and somewhere far enough away to stand, I could lift up the Earth” but how would we have calculated how much the earth actually weighs, Dave?
Dave -  Well, the simple way of doing this is because anything with a mass affects everything around it due to gravity. If it’s something roughly spherically symmetrical, you can assume that all the mass is in the centre of the planet and it behaves as if it was all the mass is right in the centre, due to some neat bits of maths. Basically, what you have to do is - if you know how much gravitational force a kilogram of anything will apply to another kilogram of anything, and you know how much force a kilogram of substance is being attracted to the Earth and you know how big the Earth is, you can work out how much mass must be in the Earth. The second part of that is really easy. Working out how much force a kilogram produces is really difficult because it’s about 10-11 Newtons at a metre between 2 kilograms. It’s an incredibly tiny force and it wasn’t done until near the end of 19th century.
Chris -  Henry Cavendish, wasn’t it?
Dave -  Yup. Indeed and you can work it out, and then from that, you can work out how heavy the Earth is, and from that, how heavy everything else is in the universe really.
Click to visit the show page for the podcast in which this question is answered. Alternatively, [chapter podcast=2913 track=10.11.28/Naked_Scientists_Show_10.11.28_7576.mp3] listen to the answer now[/chapter] or [download as MP3]
« Last Edit: 10/12/2010 15:26:06 by _system »

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Offline CPT ArkAngel

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« Reply #20 on: 01/12/2010 04:24:22 »
For me, the weight of the earth is equal to mine. I can feel it right now... [???]

The weight is a force : F = m * g
« Last Edit: 01/12/2010 04:26:25 by CPT ArkAngel »

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Offline Foolosophy

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« Reply #21 on: 01/12/2010 08:43:16 »
(is the earth accelerating around the sun? so from your own Newtonian equation a=0 so F=0,)

The earth is by definition in free fall motion/orbit around the sun

The earth's weight is therefore equal to zero = ie its like being in a weightless environment

The mass of the earth is an intrinsic property of the earth and is constant

(although relativity tells us that mass itself is subject to relativistic effects - for example, the rest mass is different from when the same body is moving - but thats another thread topic)


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Offline imatfaal

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« Reply #22 on: 01/12/2010 10:11:17 »
Foolosophy - yes the earth is accelerating (it's in circular motion; it must be accelerating) a≠0 F≠0.  I agree with the Arkangel - although I think it weighs as much as me rather than as much as him
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

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Offline Foolosophy

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« Reply #23 on: 01/12/2010 11:02:11 »
do you know why there is weightlessness on an orbiting satellite?

Answer that question and you will understand why the weight of the earth is equal to zero

Weight is a different concept to Mass

(as far as your claim that the earth is accelerating you must remember that acceleration is the change in velocity (ie dv/dt)

how is the earths velocity changing?)
« Last Edit: 01/12/2010 11:04:34 by Foolosophy »

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Offline Foolosophy

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« Reply #24 on: 01/12/2010 12:14:28 »
Foolosophy - yes the earth is accelerating (it's in circular motion; it must be accelerating) a≠0 F≠0.  I agree with the Arkangel - although I think it weighs as much as me rather than as much as him

So you are claiming that the earth's velocity is changing??

what is driving this dv/dt and in what direction is it occuring?


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Offline imatfaal

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« Reply #25 on: 01/12/2010 12:32:33 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps. 
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

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Offline Foolosophy

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« Reply #26 on: 01/12/2010 12:48:18 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps. 
you are still claiming that the earth has weight because its accelerating????

Its a physical fact that the weight of the earth is exaclty equal to zero

reason?? because its in free fall motion around the sun

Its the same reason why astronauts are weightless in orboting space stations

are you disputing these facts?

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Offline Foolosophy

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« Reply #27 on: 01/12/2010 12:52:43 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps. 

Are you still claiming that the earth has a value for WEIGHT?

The fact is that the earth is in free fall motion around the sun and so its weigth is equal to exactly zero - its weightless.

Why do astronauts experience weightlessness in orbiting space stations?

Are you disputing this simple high school physics assigment?
« Last Edit: 01/12/2010 12:54:25 by Foolosophy »

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Offline QuantumClue

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« Reply #28 on: 01/12/2010 13:56:33 »
Foolosophy - perhaps if you spent a moment with a basics physics text or even on wikipedia; the recommended reading topic is vector quantities with reference to velocity and acceleration  (magnitude and direction).  You will soon learn that scalars such as speed are not same as vectors such as velocity.  Both forms of reference will also have a section on circular motion - that will fill the most obvious gaps. 

Are you still claiming that the earth has a value for WEIGHT?

The fact is that the earth is in free fall motion around the sun and so its weigth is equal to exactly zero - its weightless.

Why do astronauts experience weightlessness in orbiting space stations?

Are you disputing this simple high school physics assigment?
I don't think this is technically correct. This is the kind of thing taught in freshmen college, but a deeper understanding of F=Mg suggests otherwise.

F=Mg still applies in space. Technically, astronauts still have a weight because there are gravitational forces acting on the particles of their bodies.

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Offline QuantumClue

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« Reply #29 on: 01/12/2010 14:50:23 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

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Offline imatfaal

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« Reply #30 on: 01/12/2010 15:45:34 »
Foolosophy

Firstly - you seem to have drawn back from your claims that the earth isn't accelerating, glad to see you have read up on vectors v scalars and circular motion.  Secondly, you need to understand what free-fall means. 

Free-fall motion is when the only force experienced is that of gravitational attraction.  We feel gravitational attraction on earth - but on earth there is also a normal force (equal and opposite) from the ground; this is why we don't sink through the floor. 

Astronauts in a space station are in orbit - they are in freefall, but it is completely incorrect to say that there is no gravitational attraction towards the earth.  If they were not continually accelerating (due to a force) towards the earth they, and their tin can, would fly off at a tangent.  They weigh something (not as much, but something) in space just as much as they do when they jump in the air when back on planet earth.  Just because there is no normal at an instant in time does not mean that there is no attraction/force - it is that their attraction to the earth is counteracted in a different manner than the normal force that we suffer.
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

At the surface, we may appear as intellects, helpful people, friendly staff or protectors of the interwebs. Deep down inside, we're all trolls. CaptainPanic @ sf.n

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Offline Foolosophy

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« Reply #31 on: 01/12/2010 22:04:21 »
Foolosophy

Firstly - you seem to have drawn back from your claims that the earth isn't accelerating, glad to see you have read up on vectors v scalars and circular motion.  Secondly, you need to understand what free-fall means. 

Free-fall motion is when the only force experienced is that of gravitational attraction.  We feel gravitational attraction on earth - but on earth there is also a normal force (equal and opposite) from the ground; this is why we don't sink through the floor. 

Astronauts in a space station are in orbit - they are in freefall, but it is completely incorrect to say that there is no gravitational attraction towards the earth.  If they were not continually accelerating (due to a force) towards the earth they, and their tin can, would fly off at a tangent.  They weigh something (not as much, but something) in space just as much as they do when they jump in the air when back on planet earth.  Just because there is no normal at an instant in time does not mean that there is no attraction/force - it is that their attraction to the earth is counteracted in a different manner than the normal force that we suffer.

I am astonished at the polemic here.


The weight of the earth = 0 for the same reason that astronauts are weightless when orbiting the earth in a space station - THEY ARE IN FREE FALL MOTION

Now if you don't like this reality all I can suggest is to take up the matter with Sir Isaac Newton's estate.

ARE you still claiming that the earth's weight ISNT equal to zero??

Perhaps you can use your scalarisation and vectoring techniques to prove your alchemic claim?


« Last Edit: 02/12/2010 00:04:10 by Foolosophy »

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Offline Foolosophy

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« Reply #32 on: 01/12/2010 22:23:12 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

The F=ma equation is in relation to an accelerating body.

The gravitational force between two bodies can be determined by Newtons law


where G is the universal gravitational constant = 6.67*10^-11 (Nm^2/kg^2)

(G is just a phyisical constant, its not the same as the "g" in F=mg - you're confusing the two)

For example, when pilots experience g forces in their planes, say 4g, it means that the force they are experiencing is 4 times that of the earths normal gravitational pull.
« Last Edit: 02/12/2010 00:05:18 by Foolosophy »

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Offline Foolosophy

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« Reply #33 on: 02/12/2010 01:20:10 »
"imatfaal" wishes to discuss the centrifugal force of a body in circular motion


(And remember the orbit of the earth around the sun isnt strictly circular - its eliptical, but what's a few focii amongst friends hey?)

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Offline Foolosophy

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« Reply #34 on: 02/12/2010 01:22:04 »
the centripetal force is a different thing again


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Offline Foolosophy

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« Reply #35 on: 02/12/2010 01:24:45 »
But most importantly though, Imatfaal needs to acknowledge the fact that the weight of the earth is equal to zero

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Offline QuantumClue

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« Reply #36 on: 02/12/2010 02:15:56 »
For instance, usually in very elementary physics, weight is the force exerted on a mass. The acceleration ''g'' is not zero in space. So setting g=0 for W=Mg is not exactly correct. It is true we experience weightlessness, but there is some debate as to whether this is technically correct.

The F=ma equation is in relation to an accelerating body.

The gravitational force between two bodies can be determined by Newtons law


where G is the universal gravitational constant = 6.67*10^-11 (Nm^2/kg^2)

(G is just a phyisical constant, its not the same as the "g" in F=mg - you're confusing the two)

For example, when pilots experience g forces in their planes, say 4g, it means that the force they are experiencing is 4 times that of the earths normal gravitational pull.

No offense, but you really do need to work on your units. Yes (a) is acceleration, but g is also an acceleration. This relationship is true. Weight W is also the dimensions of a force exerted on an object.

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Offline QuantumClue

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« Reply #37 on: 02/12/2010 02:19:10 »
Learn here:

Equations for a falling body - Wikipedia, the free encyclopediaFor example, Newton's law of universal gravitation simplifies to F = mg, ...
en.wikipedia.org/wiki/Equations_for_a_falling_body - Cached - SimilarShow more results from wikipedia.org

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Offline Foolosophy

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« Reply #38 on: 02/12/2010 02:47:17 »
Learn here:

Equations for a falling body - Wikipedia, the free encyclopediaFor example, Newton's law of universal gravitation simplifies to F = mg, ...
en.wikipedia.org/wiki/Equations_for_a_falling_body - Cached - SimilarShow more results from wikipedia.org

...are you saying that the earth is NOT weightless?

I am not saying that the earth is massless (its mass is an instrinsic property)

I am just saying that the earth is in free fall motion aroudnd the sun - so its weight is equal to zero

Similar to being weightless in a space station that is orbiting the earth in free fall motion

Weight and Mass are not equivalent

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Offline maffsolo

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« Reply #39 on: 02/12/2010 03:48:30 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

http://www.physlink.com/education/askexperts/ae321.cfm
=============================

Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?


 [attachment=13500]


http://en.wikipedia.org/wiki/Gravitational_constant

Hmmmm no mention of weight there....



« Last Edit: 02/12/2010 04:01:32 by maffsolo »

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Offline Foolosophy

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« Reply #40 on: 02/12/2010 04:01:58 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

http://www.physlink.com/education/askexperts/ae321.cfm
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Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?


So you agree that the earth is in free fall motion around the sun and therefore its weight is equal to ZERO??

Why are astronauts weightless in space stations that are orbiting the earth?

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Offline maffsolo

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« Reply #41 on: 02/12/2010 04:28:44 »
What is the difference between mass and weight?

Mass is a measure of how much matter an object has. Weight is a measure of how strongly gravity pulls on that matter. Thus if you were to travel to the moon your weight would change because the pull of gravity is weaker there than on Earth but, your mass would stay the same because you are still made up of the same amount of matter.

Answered by: A. Godbehere, High School Student, Port Perry

Imagine yourself out is space away from any gravitational field, with a bowling ball in your hands. Let it go and it just floats in front of you. Without gravity, it has no weight. Now grab it again and shake it back and forth. That resistance to being moved is inertia, and mass measures how much inertia an object has. Inertia does NOT depend on gravity.

Mass is determined only by the amount of matter contained in an object.

Any two masses exert a mutual attractive force on each other. The amount of that force is weight. A one kilogram mass on the Earth's surface results in 2.2 pounds of force between the mass and the Earth, so we say the mass weighs 2.2 pounds. That same one kilogram mass on the Moon, because of the Moon's lower mass, results in only about 1/3 pounds of mutual force.

Just remember that the weight of an object depends on where it is, while its mass stays the same.

Answered by: Paul Walorski, B.A., Part-time Physics Instructor

http://www.physlink.com/education/askexperts/ae321.cfm
=============================

Ironic that weight is always referenced to a surface ground plane ...

So what ground plane is the Earth's weight   referenced to ????

I have heard the that a free fall in space still has Micro Gravity, what is meant by that?

Is it earth's gravity affect on the freefall?


So you agree that the earth is in free fall motion around the sun and therefore its weight is equal to ZERO??

Why are astronauts weightless in space stations that are orbiting the earth?

Yea how can you weigh the earth against the earth.

I kind of like learning to staying away from the association of the words "weightless" with "freefall" in the same breath...
Reason being, it is easy to misinterpret the slang...

"There is no gravity in space."  FALSE  If there were no gravity in space, the space shuttle would not be able to orbit the Earth, the moon would not orbit the Earth, and the Earth would not orbit the Sun.  The reason we tend to think of there being no gravity in space is that we have seen movies of the astronauts being "weightless".  They aren't actually weightless, they are still being pulled down by gravity but they and the space shuttle are in a constant state of freefall around the Earth.  So they seem to be weightless as a result of the falling - just as you would seem weightless if you were in an elevator when the cable broke.

http://www.regentsprep.org/regents/physics/phys01/unigrav/default.htm

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Offline Foolosophy

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« Reply #42 on: 02/12/2010 04:39:41 »
maffsolo

what is the weight of the astronauts in the spcae stations when they are orbiting the earth in free fall motion?

They are weightless - their mass doesnt change (although strictly speaking their relativistic masss does change when compard to their rest mass - but that is neglible for the speed that they are travelling at and really a topic for another thread)

I doubt whether you can find a physicist in the world today that would dispute the fact that the earth is weightless as it orbits the sun.

I am just responding to the actual question posed in this thread - and it asks what the earth WEIGHS - not its mass.
« Last Edit: 02/12/2010 04:53:22 by Foolosophy »

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Offline maffsolo

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« Reply #43 on: 02/12/2010 04:58:42 »
maffsolo

what is the weight of the astronauts in the spcae stations when they are orbiting the earth in free fall motion?

They are weightless - their mass doesnt change (although strictly speaking their relativistic masss does change when compard to their rest mass - but that is neglible for the speed that they are travelling at and really a topic for another thread)

I doubt whether you can find a physicist in the world today that would dispute the fact that the earth is weightless as it orbits the sun.

I am just responding to the actual question posed in this thread - and the it asks what the earth WEIGHS - not its mass.
I see your point!

I believe you can mathmatically hypothisize a value that can represent a weight.
In saying that, I also contest that, that value has no scientific value except for saying wow thats heavy.

We can hypthetically evaluate...

We know the earths mass we know the earths gravitational acceleration.
Let's just say we like to know, if an object was the same mass of the earth and it were sitting on the surface of the earth, hypothetically speaking, how much will the object weigh?
« Last Edit: 02/12/2010 05:11:38 by maffsolo »

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Offline Geezer

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« Reply #44 on: 02/12/2010 05:02:01 »
It would certainly be quite hard to find bathroom scales that were capable of weighing it. Boots maybe?

You'd also need a really big bathroom.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Foolosophy

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« Reply #45 on: 02/12/2010 06:48:03 »
-----------------------------------------------------------------------------------------
[/quote]
We can hypthetically evaluate...

We know the earths mass we know the earths gravitational acceleration.
Let's just say we like to know, if an object was the same mass of the earth and it were sitting on the surface of the earth, hypothetically speaking, how much will the object weigh?
[/quote]
----------------------------------------------------------------------------------------------

what do you mean by the "earth's gravitational acceleration"??? g?

You can hypothecise all you wish but the question in htis thread is "how much does the earth weigh"

the answer is zero because the earth is in free fall motion around the sun

What is the weight and mass of an astronaut on a free falling space station?

What is the weight of a pilot under 4g flight conditions?

When you jump from an aeroplane with a parachute (hopefully) and you reach a terminal velocity (ie stop accelerating) your weight is equal to zero - you are experiencing weightlessness.

If you want to put another earth on top of our earth and weigh it you can - but both earths will be weightless as they hurl around the sun

I dont understand why people are disputing this in here?

Its just a definition thing


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Offline Geezer

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« Reply #46 on: 02/12/2010 07:08:40 »
Its just a definition thing


It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.
« Last Edit: 02/12/2010 07:12:51 by Geezer »
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Foolosophy

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« Reply #47 on: 02/12/2010 07:36:42 »
Its just a definition thing


It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?

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Offline Geezer

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« Reply #48 on: 02/12/2010 07:55:16 »
Its just a definition thing


It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?


I really don't know if I'm disputing any facts or not.

Weight is a measure of gravitational attraction due to mass. The Moon and the Earth can be weighed against each other, therefore, they are not weightless. (If you can find an alternative definition for weight, you should be able to prove me wrong.)
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Foolosophy

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« Reply #49 on: 02/12/2010 08:01:09 »
Its just a definition thing


It's more fundamental than that. Mass is a property of matter. Weight is a measure of the interaction between matter.

I suppose it's possible to weigh the Earth on a sort of beam balance if you compare it with the mass of the Sun, or the Moon. For example, we might say that the Earth has a weight of x Moons. We should be able to determine the null point of the fulcrum from the Earth's Lunar wobble.

Its not about weighing the earth whilst its static

THe question is "what is the weight of the earth"?

Are you disputing the fact that the earth's weight is equal to zero?


I really don't know if I'm disputing any facts or not.

Weight is a measure of gravitational attraction due to mass. The Moon and the Earth can be weighed against each other, therefore, they are not weightless. (If you can find an alternative definition for weight, you should be able to prove me wrong.)

This is incorrect reasoning (if you dont mind me being abrupt)

The moon is also in free fall motion aroudn the earth so its weight is zero also.

If you weighed yourself on earth and then on the moons surface the weight values will differ (by a factor of 6). But you are not in free fall motion when youre being weighed.

Its to do with the fact that the earth is in free fall orbit around the sun - just like a space station orbiting the earth