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Apr 10, 2021, 5:40:14 AM4/10/21

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In the formula F=ma force is related to acceleration.

If acceleration exists in all references, the force is real, otherwise,

if it exists in one reference and "disappears" in the other, then the

force is "apparent".

On the other hand, in the formula F=m1*m2/d^2 there is NO acceleration

and this is the difference between the second formula and the previous

one.

In F=m1*m2/d^2 the force depends exclusively on the presence of the two

masses m1 and m2 (which always exist) and on the square of their

distance (which always exists).

Therefore, if the masses m1 and m2 and the distance d^2 never disappear

(in any reference) the force F=m1*m2/d^2 is always real.

And what is the force F=m1*m2/d^2? It's gravity.

So gravity is not "apparent" because (the formula says so and not me)

its force does not disappear by changing the SDR.

If acceleration exists in all references, the force is real, otherwise,

if it exists in one reference and "disappears" in the other, then the

force is "apparent".

On the other hand, in the formula F=m1*m2/d^2 there is NO acceleration

and this is the difference between the second formula and the previous

one.

In F=m1*m2/d^2 the force depends exclusively on the presence of the two

masses m1 and m2 (which always exist) and on the square of their

distance (which always exists).

Therefore, if the masses m1 and m2 and the distance d^2 never disappear

(in any reference) the force F=m1*m2/d^2 is always real.

And what is the force F=m1*m2/d^2? It's gravity.

So gravity is not "apparent" because (the formula says so and not me)

its force does not disappear by changing the SDR.

Apr 10, 2021, 2:45:53 PM4/10/21

to

In article <s4qdb4$1tfg$1...@gioia.aioe.org>, Luigi Fortunati

reference frame

> On the other hand, in the formula F=m1*m2/d^2 there is NO acceleration

> and this is the difference between the second formula and the previous

> one.

It looks like you forgot the gravitational constant; that gives the

right-hand side the dimensions of ma.

> In F=m1*m2/d^2 the force depends exclusively on the presence of the two

> masses m1 and m2 (which always exist) and on the square of their

> distance (which always exists).

And on the gravitational constant.

> Therefore, if the masses m1 and m2 and the distance d^2 never disappear

> (in any reference) the force F=m1*m2/d^2 is always real.

Acceleration is always "real". (That is actually still a puzzle:

acceleration relative to what? As far as I know, no-one has ever shown

quantitatively that Mach's principle can explain that.)

> And what is the force F=m1*m2/d^2? It's gravity.

Right, which is why the expression usually includes the gravitational

constant.

> So gravity is not "apparent" because (the formula says so and not me)

> its force does not disappear by changing the SDR.

An acceleration is real; you can feel it. You can find an accelerating

reference frame and transform it away (at least locally).

The essence of general relativity is that gravitation, in some sense, IS

acceleration, but as far as I know no-one knows why the gravitational

constant has a non-zero value or has the value it has (apart from

weak-anthropic explanations).

<fortuna...@gmail.com> writes:

> In the formula F=ma force is related to acceleration.

>

> If acceleration exists in all references, the force is real, otherwise,

> if it exists in one reference and "disappears" in the other, then the

> force is "apparent".

You can always transform an acceleration away by using an accelerating
> In the formula F=ma force is related to acceleration.

>

> If acceleration exists in all references, the force is real, otherwise,

> if it exists in one reference and "disappears" in the other, then the

> force is "apparent".

reference frame

> On the other hand, in the formula F=m1*m2/d^2 there is NO acceleration

> and this is the difference between the second formula and the previous

> one.

right-hand side the dimensions of ma.

> In F=m1*m2/d^2 the force depends exclusively on the presence of the two

> masses m1 and m2 (which always exist) and on the square of their

> distance (which always exists).

> Therefore, if the masses m1 and m2 and the distance d^2 never disappear

> (in any reference) the force F=m1*m2/d^2 is always real.

acceleration relative to what? As far as I know, no-one has ever shown

quantitatively that Mach's principle can explain that.)

> And what is the force F=m1*m2/d^2? It's gravity.

constant.

> So gravity is not "apparent" because (the formula says so and not me)

> its force does not disappear by changing the SDR.

reference frame and transform it away (at least locally).

The essence of general relativity is that gravitation, in some sense, IS

acceleration, but as far as I know no-one knows why the gravitational

constant has a non-zero value or has the value it has (apart from

weak-anthropic explanations).

Apr 19, 2021, 2:35:24 PM4/19/21

to

On 10 Apr 2021 09:40:11 GMT, Luigi Fortunati wrote:

Let me try a simpler, and clearer, answer.

> In the formula F=ma force is related to acceleration.

I always write this formula as a=F/m in order to stress the fact that if a

force F acts on a body/particle of mass m, then the particle will get an

acceleration a given by a=F/m. This is the Newton's second law.

F is the CAUSE (of the acceleration) and a is the EFFECT. I put the effect

on the left hand side, and the cause on the right hand side,

I DO NOT take the formula F=ma to be DEFINITIONS for F !!!

In a=F/M, F is ANY force, of any nature, coming from various sources, for

example:

- a spring acting on the body or particle: k*x (x is the displacement from

the equilibrium position

- a rope - F = tension in the rope

- a surface with which the body is in contact

- an static electric force (Coulomb) Q1*Q2/d^2

- or gravitational force: m1*m2/d^2

- or friction, etc.

Correspondingly, if on the body/particle acts, for example, only a spring,

then the Newton's second law gives that the acceleration will be

a=F/m=k*x/m

Please note that the Newton's second law is only valid with respect to

certain frames of reference. But about this - maybe later.

IF you believe this was useful for you, please let me know and I will

answer your questions and then I will continue.

Let me try a simpler, and clearer, answer.

> In the formula F=ma force is related to acceleration.

force F acts on a body/particle of mass m, then the particle will get an

acceleration a given by a=F/m. This is the Newton's second law.

F is the CAUSE (of the acceleration) and a is the EFFECT. I put the effect

on the left hand side, and the cause on the right hand side,

I DO NOT take the formula F=ma to be DEFINITIONS for F !!!

In a=F/M, F is ANY force, of any nature, coming from various sources, for

example:

- a spring acting on the body or particle: k*x (x is the displacement from

the equilibrium position

- a rope - F = tension in the rope

- a surface with which the body is in contact

- an static electric force (Coulomb) Q1*Q2/d^2

- or gravitational force: m1*m2/d^2

- or friction, etc.

Correspondingly, if on the body/particle acts, for example, only a spring,

then the Newton's second law gives that the acceleration will be

a=F/m=k*x/m

Please note that the Newton's second law is only valid with respect to

certain frames of reference. But about this - maybe later.

IF you believe this was useful for you, please let me know and I will

answer your questions and then I will continue.

Apr 29, 2021, 3:54:37 AM4/29/21

to

Alex <alexl...@removesolnet.ch> wrote:

> > In the formula F=ma force is related to acceleration.

> I always write this formula as a=F/m in order to stress the fact that if a

> force F acts on a body/particle of mass m, then the particle will get an

> acceleration a given by a=F/m. This is the Newton's second law.

I prefer to write: dv/dt = F/m
> > In the formula F=ma force is related to acceleration.

> I always write this formula as a=F/m in order to stress the fact that if a

> force F acts on a body/particle of mass m, then the particle will get an

> acceleration a given by a=F/m. This is the Newton's second law.

> F is the CAUSE (of the acceleration) and a is the EFFECT. I put the effect

> on the left hand side, and the cause on the right hand side,

"How to be causal: time, spacetime, and spectra",

Eur. J. Phys. 32, 1687?1700 (2011)

doi:10.1088/0143-0807/32/6/022

with a longer version at arxiv:1106.1792

Mind you, some physicsts find the proposal intensely annoying,

and they disagree with it quite strongly - despite its deliberately

limited scope (i.e. on the interpretation of temporal differential

equations). There are thus several extra appendices in the arxiv

version addressing various points raised.

#Paul

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