What is the scientific definition of a force?

In physics you deal with units. However you decide or choose which conditions you include in your theory, if you can't "recover" the physics--an actual path "s" through space, over a finite interval of time "t", there is no hope. If you "abstract away" the mass, or anything physical for some reason (why it would be or who to, are different problems), then you have to put it back to recover observational results.

In vector spaces unit vectors can replace any basis set of vectors, in that space. Force and momentum are both vectors, but are not in the same vector space(s).
In mechanics of rigid bodies in motion, mass is distributed into a volume with a shape.

One of the curious things about the moment of inertia I, is that it's related to a fixed (by the geometry and a chosen axis of rotation), radius, the radius of gyration. This is another of those geometric things about the gravitational/inertial interactions.

The radius, call it a thing defined at a boundary, a geometric condition or constraint. has a number of small volume elements somewhere along it; the problem of finding these two geometric conditions--I and the radius of gyration--is a calculus problem, finding the volume of revolution. Unless you don't have a nice ring or flat disc, you have to get geometric another way. Finding the radius of gyration gives you the moment of inertia because of a geometric relation. The mass of a rigid body with an homogenous density of matter is fixed for any small volume element you sum over.

But you need to have this mass-density relation, calculus otherwise will let you deal with a small ring as if it's a 1-torus with a lineal mass density. You recover observable physics by finding the inertial moments along this abstract 1-torus or "thin" ring. So a disc is a sum of small, concentric rings, so I for a ring is basic, or a foundation for the next composite shape, or distribution of matter, the disc, which is topologically equivalent to a bowl, which is . . .

F=ma is not circular. However, it requires that two of the three quantities be defined independently. Having done that, the third quantity is then defined by the equation.

F=ma is a NET force. If acceleration is zero then force=zero.

So I push on a brick wall and it doesn't change velocity, which means the acceleration is zero. You're trying to tell me the force=0 because the acceleration is zero?? The NET force is zero, but I am applying a force to the wall, and it is not accelerating.

James, are you still having difficulty coming to terms with what force is?

Do you need me to school you some more? You miss me don't you? Admit it!

F=ma is a NET force. If acceleration is zero then force=zero.
If acceleration is zero, then net force is zero.
So I push on a brick wall and it doesn't change velocity, which means the acceleration is zero. You're trying to tell me the force=0 because the acceleration is zero?? The NET force is zero, but I am applying a force to the wall, and it is not accelerating.
Yes, but you're not the only thing applying force to the wall. Traditionally, walls are attached to the ground, for instance.
James, are you still having difficulty coming to terms with what force is?
What do you mean "still"? It sounds to me like you're a bit confused about what "net force" means.
Do you need me to school you some more? You miss me don't you? Admit it!
Who are you?

If acceleration is zero, then net force is zero.

Right, the NET force is zero. Do you know what NET is? In a tug of war, the net force is zero when neither side is moving, but each applying 1,000 lbs of force to the rope in opposite directions. Zero net force, and zero acceleration. But the rope could break!

Yes, but you're not the only thing applying force to the wall. Traditionally, walls are attached to the ground, for instance.

So you think the wall is applying a force to me? I am applying motion to the wall, and the wall is resisting my motion, which creates force. Force is created by a resistance to motion. The wall is not applying a force to me, it is a resistance to my motion.

What do you mean "still"? It sounds to me like you're a bit confused about what "net force" means.

You never mentioned net until I mentioned it. F=ma is a NET FORCE, and you know what net means, right?

Who are you?

The creator of MD's Box! Duh?

Right, the NET force is zero. Do you know what NET is?
Yes. The net force on an object is the vector sum of all of the forces acting on that object.
In a tug of war, the net force is zero when neither side is moving, but each applying 1,000 lbs of force to the rope in opposite directions. Zero net force, and zero acceleration. But the rope could break!
It sounds like you're considering the two teams and the rope as if it were a single object. In that case, what you say is fine, as long as we understand that we're talking about the net external force on the system (zero in your example, where there is no acceleration). In this picture, forces on the rope are internal forces. The rope is only able to withstand a certain tension force. If that is exceeded, it will certainly break.
So you think the wall is applying a force to me?
Yes. Newton's 3rd law: for every action there is an equal an opposite reaction on some other object. You push on the wall; the wall pushes back on you with an equal force in the opposite direction. If that force wasn't there, you'd fall through the wall.
I am applying motion to the wall, and the wall is resisting my motion, which creates force.
Motion is the result of a force, not the cause of it.
Force is created by a resistance to motion.
Hmmm.... maybe.

F=ma. The "m" in that equation is a measure of the inertia (resistance to motion) that the system/object has. To accelerate the object, a (net) force must be applied. The resulting acceleration will be directly proportional to the force and inversely proportional to the mass (inertia).
The wall is not applying a force to me, it is a resistance to my motion.
Yes it is. Newton's 3rd law. See above.
You never mentioned net until I mentioned it.
F=ma is a NET FORCE, and you know what net means, right?
Yes. See above.
The creator of MD's Box! Duh?

Last seen at sciforums in 2014. You asked to be permanently banned, I believe (?) I wasn't the one who handled your request.

How are things? Why return now?

Last seen at sciforums in 2014. You asked to be permanently banned, I believe (?) I wasn't the one who handled your request.

How are things? Why return now?

Things are about par for the course. Being retired I do what I want, and have all the time in the world.

I still visit this place just about every day, mainly to get a laugh, but to learn a thing or two here and there. Not much good content here for the past decade.

I couldn't control myself when I saw Neddy Bate's comment about me. I always liked Neddy, we had some good debates and he taught me a lot.

So I figured I would drop in and say hi. Plus I had to rattle your cage a little. Good times!

I still visit this place just about every day

That's a surprise. How have you managed to resist the temptation to post anything for 8 years?

That's a surprise. How have you managed to resist the temptation to post anything for 8 years?

I have a strong mind. I quit smoking cold turkey after a pack a day for 26 years. I just made up my mind I was not gonna smoke any more, and that was that. Never looked back.

I figured with this place it was worth getting banned again to say hi to Neddy.

James, you should go to https://ilovephilosophy.com/ and debate me on some stuff.

Maybe you are already there? From time to time I get a "James R." vibe from different people. There is one there now that seems to be just like you. I won't mention any names.

Last edited by a moderator:
I figured with this place it was worth getting banned again to say hi to Neddy.
Well, you're here for now, anyway. Didn't you ask to be banned, previously?
James, you should go to https://ilovephilosophy.com/ and debate me on some stuff.

Maybe you are already there? From time to time I get a "James R." vibe from different people. There is one there now that seems to be just like you. I won't mention any names.
I'm not there and have not been there. Just so we're clear. If there are any fanboy impersonators, I'd love to know. Flattering!

Well, you're here for now, anyway. Didn't you ask to be banned, previously?

Yes, I asked to be banned permanently because I was sick and tired of being temporarily banned for petty BS just to shut me up. Every time I turned around I was getting banned for some stupid petty BS, so I just requested a permaban, and it was granted. It was obvious I was not welcome here, so I left! How's the place been since then? Everyone leave? This place was rockin' with AN, Farsight, Neddy, rpenner, and tons of other people. It's dead now!

Yes, I asked to be banned permanently because I was sick and tired of being temporarily banned for petty BS just to shut me up. Every time I turned around I was getting banned for some stupid petty BS, so I just requested a permaban, and it was granted. It was obvious I was not welcome here, so I left!
Fair enough. If the vibe of the place doesn't suit you, for whatever reason (including how moderation is done), then it makes good sense to leave. I congratulate you, since so many other people seem to have huge struggles with that particular idea.
How's the place been since then? Everyone leave? This place was rockin' with AN, Farsight, Neddy, rpenner, and tons of other people. It's dead now!
Membership has dropped off quite a bit, I think - talking about active members here. Probably they are all on social media, or having lives or something. [Ha! You can have your so-called "lives", you dirty rats! We'll see who is laughing when the apocalypse comes! Bwhahaha! ..... ahem. Excuse me. I don't know what came over me.]

You can have your so-called "lives",
My life was great

Had great female company in Bali

Extremely fortunate being with the girl I was with when I became stranded (ended up being for 18 months)

Appointed herself myself sponsor, guided me though Indonesian rules and regulations

Even after a ton of paperwork obtained for me first vaccinate against COVID-19 which was accepted ligit when I got back Australia

Now trying to get back to be her sponsor to come Australia

[Ha! You can have your so-called "lives", you dirty rats! We'll see who is laughing when the apocalypse comes! Bwhahaha! ..... ahem. Excuse me. I don't know what came over me.]

Are you the one posting "Jesus is coming" signs on the side of the road?

How can a force physically exist? How can there be a pushing or a pulling in empty space without something there doing the pushing and pulling? IOW, how can there exist a pure action at a distance? And what is the medium of a force's transmission in empty space?
A true force requires a field particle mediator. Gravity Interestingly doesn't have one from first principles of it being a pseudoforce in GR. So gravity isn't exactly a force per se, which would answer why we can't unify it like a quantum field.

Semi classical gravity all the way!

A force is a vector.

Yes, historicaly, but you can understand it more generaly as : The "thing" that can (will) change something.
A force is not only associated with motion but can even be associated with "breaking" (changing) something.
Force is what physicists refer to, as soon as they observe a change : It is the technical term of this manifestation of the real.

Yes, historicaly, but you can understand it more generaly as : The "thing" that can (will) change something.
A force is not only associated with motion but can even be associated with "breaking" (changing) something.
Force is what physicists refer to, as soon as they observe a change : It is the technical term of this manifestation of the real.
This is nonsense.