# What exactly is a force?

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#### @/antic

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##### What exactly is a force?
« on: 27/07/2012 20:54:50 »
Is it always an interaction between particles?

Cheers
Atlantic

#### pinballed

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• 17
##### Re: What exactly is a force?
« Reply #1 on: 27/07/2012 22:26:38 »
Is it un-polite to build on a question? If so neglect this...
I think this question is very interesting, and have understood that it is an interaction between particles with the current definition of force.

But particles make this interaction often (always?) with messenger particles that does not carry the force
but rather the information. In electromagnetic force the messenger particle is a photon, and it is "used"
both to signal attraction as well as repulsion. How?
And to the original question, what is REALLY force?

Polarized energy? And What is energy? Guess nobody knows??

#### Voxx

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• 192
##### Re: What exactly is a force?
« Reply #2 on: 28/07/2012 03:21:11 »
Is it always an interaction between particles?

Cheers
Atlantic

Q: What exactly is a force?
A: Force is the Strength or energy as an attribute of physical action or movement.

Q: Is it always an interaction between particles?
A: This is a bit more of an interesting question, Is force always an interaction between particles?  We see this movement or action of force because the said "force" is in process through these particles.  Although, interaction with particles and force are completely different within my knowledge, but are closely related to each other because of the correlation between the two interactions.

I guess what I'm trying to get at is, force is observable because of the interactions of particles.

As to photon's attracting and repelling; the photon repels each other because they are the same, but attract electrons because they are different.  If i'm getting the drift of that question.

Polarization: Polarization is a phenomenon in which waves of light or other radiation are restricted in the direction of vibration.

What is energy: Energy is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems.  Make sense?

This is what I understand and I may be completely wrong, so correct me with what is needed.

#### Pmb

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• Physicist
##### Re: What exactly is a force?
« Reply #3 on: 29/07/2012 19:16:28 »
Is it always an interaction between particles?

Cheers
Atlantic
I think of force as being defined as the time rate of change of momentum. i.e. F = dp/dt. In some cases a particular force can be expressed in terms of the gradient of a potential, i.e.

$$F = -\nabla \Phi$$

The equation of motion then becomes

$$\frac{dp}{dt} = -\nabla \Phi$$

#### Geezer

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##### Re: What exactly is a force?
« Reply #4 on: 29/07/2012 20:09:45 »

Is it always an interaction between particles?

You can only detect a force by interaction with particles, but whether forces are conveyed by particles is the subject of a lot of on-going research.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

#### yor_on

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##### Re: What exactly is a force?
« Reply #5 on: 29/07/2012 21:52:55 »
And if is a field?

We need some stuff to make a 'force', we need distance, we need 'time'. Then we need 'objects' that interact in some way, then we need 'force carriers' of some kind, something that tells B that A did it, and 'action and reaction'. When you throw a pebble in the pond you get waterings traveling in a medium, if the water would be the field, what makes the rings.
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