Metric - kg or N

[JAE]

I have an international exchange student working with us this summer who is a graduate engineer from Venezuela.We were discussing the applications of the English vs. Metric units in the U.S. and she indicated that all calculations and references for force units in Venezuela were based on kg (kg/m^2, kg/m, etc.) and they never use Newtons or Pascals.

All of the current GSA, DOT, and Corps of Engineers data we have indicate that Newtons and Pascals (for stress) are the proper usage.Is there some rationale for using kg in calcs? Note that AISC metric shapes are indicated in kg/m units.

The only concept we came up with is that you should stay in either kg or N consistently based on whether or not your specification or code provides limits on stresses in k/m^2 or in Pascals.

 

[Ron]

Accepted SI application convention is Newtons and pascals, with their appropriate prefixes.&nbsp;&nbsp;This is what I am teaching in construction/engineering coursework and in my consulting activities.<br><br>I agree that fundamentally it makes no difference as long as consistency prevails.

 

[Ginger]

In the UK we use Newtons and either Pascals or Newtons per square millimetre.&nbsp;&nbsp;The deign codes in the UK and across Europe use these units, although, as Ron states, whichever you use, consistency is the key.<br><br>regards<br> <p>Andy Machon<br><a href=mailto:Andy@machona.freeserve.co.uk>Andy@machona.freeserve.co.uk</a><br><a href= > </a><br>

 

[babe]

kg is the unit for mass, N is the unit for force, see Newton's law.<br>Using kgf for force is outdated and considering the messages above confusing.

 

[legner]

I believe sometimes they use kilogram as a force by assuming earth's gravity, i.e. 1 kgf = 9.81 N. This is analogous to using pounds for mass rather than slugs.<br>

 

[cv]

In fact unity sistems before SI did not pay much atention to the efect of gravity.<br>I think that in Venezuela they still use the so called technical system of unities like in the old Germany, designated as MKpS ( meter, kilograme weigth and second ).<br>Nowadays the countries all around the world subscribed a convention to addopt and use forever the SI unities, I am sure even the USA had subscribed that, but as it is a strong market is still keeping in use the Imperial system of unities. <p>CV<br><a href=mailto:carlosvalinhas@netcabo.pt>carlosvalinhas@netcabo.pt</a><br><a href= > </a><br>

 

[engcomp]

I agree with Ron that consistency is all that matters. Since the rest of the world uses Newtons and its appropriate derivatives (kN, kPa, MPa etc.), the SI system is the one to use.<br><br>When you make the change as I did twice - firstly from the old European system of kg as a force to the old British system of lbs and inches and feet; secondly to the SI system when it was introduced in Australia - you will experience a brief period of discomfort.<br><br>Before long, you will forget the old system and relish the new one with its clear distinction between mass and force.

 

[ok]

It is of no any problem to use this or this units as we are understandig the meaning of them and the diversion formula&nbsp;&nbsp;n , kn , pascal&nbsp;&nbsp;are used in countries which are using foot&nbsp;&nbsp;inch base&nbsp;&nbsp;in calculation&nbsp;&nbsp;but in countries which are using meter and cms. they are using the matching force units kg., ton. which is equal to 1000 kgms.&nbsp;&nbsp;nevertheless there is a relation amog all these units&nbsp;&nbsp;like&nbsp;&nbsp;1000 kn=100 ton (metric ton ) approximately and can be calculated exacly by knowing&nbsp;&nbsp;the gravity acceleration value in the two units.