Push gravity hijack from gravity, push or pull

[Eise]

Sir Isaac's law of mutual attraction says nothing about a maximum force when the masses are equal. The law says for any two masses. Your argument is a mass of 9 and 1 have lesser attraction than masses of 8 and 2. Why?

 

Because 1 x 9 = 9 and 2 x 8 = 16.

Last time I looked 16 > 9.

 

[stupidnewton]

 

 

Because that's how math works.

 

There's no contradiction because there is no legitimate reason to think the attraction would be constant if you re-distribute the masses.

Since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled. If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on.

 

More massive objects attracting each other with greater gravitational force says the total amount of mass present is the determiner of the gravitational force.

 

Sorry. There is no other way of looking at it. Saying there is no legitimate reason to think the attraction would be constant if the distribution is altered does not answer why the attraction does alter with distribution.

 

What is the physics of the "that's way maths works"? If you don't know, you don't understand the law.

Edited December 9, 2016 by stupidnewton

[Strange]

 

More massive objects attracting each other with greater gravitational force says the total amount of mass present is the determiner of the gravitational force.

 

 

Right. So that is why we have [latex]\displaystyle f = G \frac {M_1 + M_2}{r^2}[/latex]

 

Oh, except we don't. That equation would give the wrong results. On the other hand, Newton's equation works pretty well.

 

 

 

Since the gravitational force is directly proportional to the mass of both interacting objects,

 

And that is only possible if the force is proportional to the product of the masses.

Because that's how math works.

 

And, apparently, pretty much how reality works as well.

Edited December 9, 2016 by Strange

[swansont]

Since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. So as the mass of either object increases, the force of gravitational attraction between them also increases. If the mass of one of the objects is doubled, then the force of gravity between them is doubled. If the mass of one of the objects is tripled, then the force of gravity between them is tripled. If the mass of both of the objects is doubled, then the force of gravity between them is quadrupled; and so on.

 

More massive objects attracting each other with greater gravitational force says the total amount of mass present is the determiner of the gravitational force.

 

Sorry. There is no other way of looking at it. Saying there is no legitimate reason to think the attraction would be constant if the distribution is altered does not answer why the attraction does alter with distribution.

 

What is the physics of the "that's way maths works"? If you don't know, you don't understand the law.

 

If the mass of one object is doubled and the other is halved, the force stays constant. So if you have 10 and 2, and change this to 5 and 4, or 20 and 1, the force stays the same. All in accordance with your first observation. But clearly the mass of the system doesn't stay constant. The total mass is not a factor.

 

To say there is no other way of looking at it is preposterous. It ignores both physics and math.

[AbstractDreamer]

Since the gravitational force is directly proportional to the mass of both interacting objects

This is imprecise. Here is where your problem is.

Since the gravitational force is directly proportional to the <PRODUCT OF NOT THE SUM OF> mass of both interacting objects (assuming constant r and constant G)

 

 

IS proportional to m1 MULTIPLIED by m2

 

IS NOT proportional to m1 PLUS m2

Edited December 10, 2016 by AbstractDreamer

[Mordred]

nicely put +1

[stupidnewton]

This is imprecise. Here is where your problem is.

Since the gravitational force is directly proportional to the <PRODUCT OF NOT THE SUM OF> mass of both interacting objects (assuming constant r and constant G)

 

 

IS proportional to m1 MULTIPLIED by m2

 

IS NOT proportional to m1 PLUS m2

Rubbish. Is the gravity of the earth found by adding every mass of the earth. Or multiplying every pair of masses of the earth.

[DrKrettin]

Rubbish. Is the gravity of the earth found by adding every mass of the earth. Or multiplying every pair of masses of the earth.

 

You are confusing two totally different things.

 

1) The force of gravity that you feel on your body is proportional to the product of the mass of the Earth and the mass of your body.

 

2) The mass of the Earth is the sum of all the masses on it.

 

What is so difficult about that?

[studiot]

Rubbish. Is the gravity of the earth found by adding every mass of the earth. Or multiplying every pair of masses of the earth.

 

 

Sigh

 

In the face of such rude defiance, should I try one last time?

 

Yes you are correct in saying Newton's law states that the gravitational force between two objects is proportional to the mass of each object.

 

But that is just it.

 

It is separately and independently proportional to each mass.

 

So the force is proportional to m1 and separately proportional to m2

 

[math]F \propto {m_1}[/math]

[math]F = {k_1}{m_1}[/math]

and separately

[math]F \propto {m_2}[/math]

[math]F = {k_2}{m_2}[/math]

Arithmetically the correct arithmetical procedure to combine these two statements is to multiply not add.

 

This is because they are both contributing to F and so it is the same F in both equations.

[math]F = {k_1}{m_1}\left( {{k_2}{m_2}} \right)[/math]

[math]F = {k_1}{k_2}{m_1}{m_2}[/math]

[math]F = {k_1}{k_2}{m_1}{m_2}[/math]

we can combine the two constants in to one single constant because they are constants or scaling factors

[math]F = k{m_1}{m_2}[/math]

But we cannot do this with the masses.

It is a very important fact in physics (and maths) that if a thing is proportional to something and also (or separately) proportional to something else then it is proportional to the product (not sum) of those two somethings.

It is important because a great deal of theory is absed on this fact and the solution of many important equations also depends on it.

[AbstractDreamer]

Rubbish. Is the gravity of the earth found by adding every mass of the earth. Or multiplying every pair of masses of the earth.

The "gravity" you are referring to is an acceleration not a force.

The gravitational force I'm talking about is not the same as the "gravity" you are talking about.

 

THIS is when you sum the masses: Adding every mass of the Earth gives you the Earths total mass [math] m_{earth} [/math]. From that you can work out the gravitational field strength of the Earth

[math] g_{earth} = \frac {Gm_{earth}}{r^2} [/math].

This is 9.8 N/kg. Because the mass of most objects on Earth is negligible compared to the entire Earth, this is also the acceleration experienced by objects on Earth due to gravitational forces (gravity) in an inertial frame (from Earth as a point of rest).

This is an acceleration-due-to-gravity and it is NOT a force.

 

 

 

THIS is when you multiply the masses: The gravitational force between TWO objects is proportional to the product of their masses.

[math] F=\frac{Gm_1m_2}{r^2}[/math]

Gravitational force is what makes an elephant WEIGH more than a mouse.

 

 

 

 

[math] F=ma=mg=m_1g_{earth}=\frac{m_1Gm_{earth}}{r^2}=\frac{Gm_1m_2}{r^2}[/math]

 

[math] m_{elephant} * g_{earth} > m_{mouse} * g_{earth} [/math].

Therefore, directly, an elephant weighs more than a mouse. This gravitational force is a product of mass times acceleration-due-to-gravity. Acceleration-due-to-gravity is calculated from the Earths total mass (adding all the masses as you put it).

 

 

[math] m_{elephant} * (m_{earth}-m_{elephant}) > m_{mouse } * (m_{earth}-m_{mouse}) [/math].

The product of masses is larger for the elephant than for the mouse. This indirectly results in the elephant weighing more than a mouse (after calculating the proportional gravitational force by multiplying by G and dividing by [math] r^2 [/math])

Edited December 10, 2016 by AbstractDreamer

[DrKrettin]

I admire the last two posters for the effort they put into this.

[swansont]

Rubbish. Is the gravity of the earth found by adding every mass of the earth. Or multiplying every pair of masses of the earth.

 

 

These are different things. The "gravity of the earth" is an acceleration. To find the force between objects you have to multiply by mass of the other object, since F=ma.

[Bender]

This guy is probably just trolling but let's try a proof by contradiction, just in case:

[math] m_{elephant} * (m_{earth}-m_{elephant}) > m_{mouse } * (m_{earth}-m_{mouse}) [/math].

The product of masses is larger for the elephant than for the mouse. This indirectly results in the elephant weighing more than a mouse (after calculating the proportional gravitational force by multiplying by G and dividing by [math] r^2 [/math])

According stupidnewton, the force exerted on the elephant and the force exerted on the mouse are nearly identical, since the sum of either masses with the mass of earth does not measurably diverge from the mass of earth.

So either there is no difference between a mouse sitting on you or an elephant sitting on you, or stupidnewton is wrong. (in fact, according to stupidnewton, there is hardly a difference between a mouse sitting on you and the entire moon sitting on you)