Difference between "1 kgf" and "1 N"?

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Discussion Overview

The discussion centers around the difference between "1 kgf" (kilogram-force) and "1 N" (Newton), exploring their definitions, usage, and the implications of using non-SI units in physics. The conversation includes technical explanations, conceptual clarifications, and some historical context regarding unit systems.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants note that 1 kgf is approximately equal to 9.8 N, as it is derived from the force exerted by a mass of 1 kg under standard gravity.
  • Others express skepticism about the use of kgf in serious physics, arguing that SI units do not officially recognize it and that it leads to confusion.
  • There is a mention of the historical context of using units like poundals and the transition to SI units, with some participants advocating for a clearer understanding of force and mass.
  • Some participants question the meaning of "kilogram force," suggesting that it lacks clarity without specifying conditions, while others defend its usage as a term that exists in common discourse.
  • A reference to Wikipedia is made, stating that kgf is a non-standard unit and unacceptable in SI, which some participants believe resolves the issue, while others remain unconvinced.
  • Clarifications are provided regarding the term "g," indicating it refers to the acceleration due to gravity, not grams.
  • Some participants argue that while kgf may not be officially recognized, it is still used in certain contexts and can be explained to those unfamiliar with it.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the appropriateness of using kgf, with some advocating for its explanation and others arguing against its validity in scientific discourse. The discussion remains unresolved regarding the acceptance of kgf as a unit of force.

Contextual Notes

There are limitations in the discussion regarding the definitions of force and mass, the historical context of unit systems, and the potential confusion arising from the use of non-SI units. Some mathematical steps and assumptions about gravitational acceleration are also not fully resolved.

navneet9431
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What is the difference between 1 kgf and 1 Newton?
 
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About 10. Actually standard g, which is more like 9.8
Since f=ma
g N = 1 kg x g m/sec2
1 kg force = 1 kg x g m/sec2

Both are units of force. N is the SI unit. kg force is a non-SI unit.
 
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navneet9431 said:
1 kgf
Before getting carried away with this, where have you ever found the term "kgf" used in serious Physics? The whole point is that, in SI, Force and Mass do not share any officially named units.
When I was taught Imperial units at school, we used Poundals as the basic unit of force and lbs as Mass. If we talked about a pound force, it was frowned upon. More than fifty years later, users of Imperial units are still falling into the same sort of pitfalls. Every day, people persist with using the same sort of units that were invented when steam engines and horses and carts were the norm. Time for a serious attempt at moving to a system that was developed in a better informed era, I think. It was done successfully in UK in my lifetime (via cgs and mks) so US could easily manage it.
 
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navneet9431 said:
What is the difference between 1 kgf and 1 Newton?
I am with @sophiecentaur on this. I have been doing this stuff for decades and never seen kgf until today. I don’t know if any system of units actually officially recognizes it
 
There may be confusion because one does see the units ##\mathrm{lb}\cdot\mathrm{f}## (for reasons that may be worth discussing).
 
olivermsun said:
There may be confusion because one does see the units ##\mathrm{lb}\cdot\mathrm{f}## (for reasons that may be worth discussing).
My doubts are still unclear.
Is there no difference between "1 kilogram force" and "1 Newton"?
 
navneet9431 said:
My doubts are still unclear.
Is there no difference between "1 kilogram force" and "1 Newton"?
This was answered in post #2: the difference is 9.8kgf/N.
 
navneet9431 said:
My doubts are still unclear.
Is there no difference between "1 kilogram force" and "1 Newton"?
How can there be a "kilogram force"? The Force of a kilogram, doing what?
The 'old' system with pounds and feet was 'invented' when the weight of an object was thought to be more relevant than its mass. We know different nowadays.
russ_watters said:
This was answered in post #2: the difference is 9.8kgf/N.
I don't think so. Where does a force come from unless the conditions are properly specified? If you really feel it necessary, the term kgW (kilogram weight) would at least have some meaning, but even that is very sloppy.
 
sophiecentaur said:
How can there be a "kilogram force"? The Force of a kilogram, doing what?
...
I don't think so. Where does a force come from unless the conditions are properly specified? If you really feel it necessary, the term kgW...
https://en.m.wikipedia.org/wiki/Kilogram-force
 
  • #10
russ_watters said:
That reference tells us that " The kilogram Force is a non standard unit and is unacceptable for use in SI"
Does that resolve the issue? I know Wiki is not the fount of all knowledge.
 
  • #11
sophiecentaur said:
That reference tells us that " The kilogram Force is a non standard unit and is unacceptable for use in SI"
Does that resolve the issue?
Yes, I think it does. it's like slang; it may not be in a normal dictionary, but people still use it and it has a definition.
 
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  • #12
Merlin3189 said:
1 kg force = 1 kg x g m/sec2
What is "g" there?Is it for grams?
I have read that 1 Newton(N)= 1 kg*m/s^2
 
  • #13
navneet9431 said:
What is "g" there?Is it for grams?
No. In that context g is the standard acceleration due to gravity at the surface of the earth. So 1 g = 9.80665 m/s^2
 
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  • #14
navneet9431 said:
What is "g" there?Is it for grams?
I have read that 1 Newton(N)= 1 kg*m/s^2
No, "g" is the standard acceleration due to gravity at the surface of the earth.
 
  • #15
russ_watters said:
Yes, I think it does. it's like slang; it may not be in a normal dictionary, but people still use it and it has a definition.
I bet you wouldn’t appreciate my entering a list of other terms that fit that description and expect them to be taken seriously, though. PF normally aims at the straight and narrow path. :smile:
 
  • #16
sophiecentaur said:
I bet you wouldn’t appreciate my entering a list of other terms that fit that description and expect them to be taken seriously, though. PF normally aims at the straight and narrow path. :smile:
Please drop it. The OP asked a specific question and I gave an accurate answer. It doesn't even conflict with yours, so there is really nothing to argue about!
 
  • #17
navneet9431 said:
I have read that 1 Newton(N)= 1 kg*m/s^2

In general..

Force(N) = mass(kg) * acceleration(m/s^2)

So yes..

1N = 1kg * 1m/s^2 = 1kgm/s

However as others have said, the expression kgf isn't used in SI units. I would encourage you to forget you ever heard about kgf and make sure you can understand how to work with Newtons.

Examples...

A 1kg mass sitting on a table on Earth exerts a force of 9.8N on the table.
A 100N force accelerates a 5kg mass at 20m/s^2
 
  • #18
russ_watters said:
Please drop it. The OP asked a specific question and I gave an accurate answer. It doesn't even conflict with yours, so there is really nothing to argue about!
No argument. I'm just concerned that the OP and others shouldn't make free use of 'inappropriate' quantities or units.
 
  • #19
I don't see a problem. A poster asked a question about an unfamiliar unit that he/she may have encountered somewhere. Whether or not one likes the units, they are out there, and an explanation can be given for what the units mean along with reasons to avoid them.
 
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