Is frictional force really a force?

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Discussion Overview

The discussion revolves around the nature of frictional force, questioning whether it qualifies as a force based on its characteristics as a push or pull. Participants explore definitions of force, the role of friction in motion, and its underlying mechanisms, touching on theoretical and conceptual aspects.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory

Main Points Raised

  • Some participants assert that a force is anything that results in a change in momentum, suggesting friction fits this definition.
  • Others propose that friction acts as a transfer of momentum and is measured as a force.
  • A participant notes that friction opposes an applied force and varies depending on the direction of that force, raising the question of whether it can be classified as a force.
  • One participant emphasizes that friction is a reaction force that only exists in the presence of another force.
  • Another viewpoint suggests that friction could be considered an electromagnetic force due to interactions at the surface level, although this explanation is noted as potentially more complex.
  • Some participants express uncertainty about categorizing friction strictly as a push or pull, indicating it may exhibit characteristics of both depending on the context.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether friction can be definitively classified as a push or pull, and multiple competing views regarding its nature and definition remain present throughout the discussion.

Contextual Notes

Participants highlight limitations in defining friction based on various interpretations of force, and there is mention of the challenges in calculating frictional coefficients from first principles.

ngjingyi
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Is frictional force really a force since a force is a push or pull? Does frictional force give a push or a pull if its really a force?

Thanks
 
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A force is any thing that results in a change some thing's momentum.
 
Yes and yes.
 
thanks
 
Friction is a transfer of momentum, expressed and measured as a force.
 
D H said:
A force is any thing that results in a change some thing's momentum.
A force can also be applied with no change in momentum, such as the compression force of a vice on a spring.
 
Jeff Reid said:
A force can also be applied with no change in momentum, such as the compression force of a vice on a spring.

Or static friction.
 
ngjingyi said:
Is frictional force really a force since a force is a push or pull? Does frictional force give a push or a pull if its really a force?
I don't know if all are a push of pull, but I would think so -- friction can either be a push or a pull.
 
ngjingyi said:
Is frictional force really a force since a force is a push or pull? Does frictional force give a push or a pull if its really a force?

Thanks

Oh, oh, oh. It took me reading all eight posts, and especially watters' before I understood your question. Maybe I can rephrase what I think you are asking.

Friction opposes an applied force. As the applied force can be in either direction or even zero, the force of friction varies too. So is it a force?
 
  • #10
So pick a definition of force and see if friction fits the definition.

Newton said a body remains at rest or in a state of motion unless compelled to change by FORCES. so friction would seem to fit that definition. It always oppose motion and never aids it. KE is converted to heat.

It's an experimentally determined force (I think) and nobody has been able to calculate frictional coefficients (mu) from first principles; in other words, I know of no theory that provides the friction force between different materials.

Keeps me from falling every time I take a step, so I like it for that.
 
  • #11
It would seem to me friction is ultimately an electromagnetic force. Anytime two surfaces come in close proximity there will be repulsion between electrons. If you have a rough surface then you might encounter more of these forces that might either resist or help start the motion of an object in contact with a surface because some of these interactions will be parallel to the motion or lackthereof. Seems reasonable to me anyway. It may be much more complicated, but this appears as a reasonable cursory explanation.
 
Last edited:
  • #12
Phrak said:
Oh, oh, oh. It took me reading all eight posts, and especially watters' before I understood your question. Maybe I can rephrase what I think you are asking.

Friction opposes an applied force. As the applied force can be in either direction or even zero, the force of friction varies too. So is it a force?


yep thanks for rephrasing
 
  • #13
Whilst i think you might struggle to define friction as either a push or a pull, i think from its effects it is one or the other. I.e. on a sloope does friction push or pull you back up the slope, or both?

However I think it is most important to realize that friction is a reaction force and only exists in the presence of another push or pull.
 

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