963. Mass Property Calculations in SI Units

Paper

Abstract

The introduction in this paper discusses the necessity for the SI (System International d’Unities), and the human problem involved in changing from one system to another.
The fundamental difference between the SI and existing systems is covered. It is shown how the SI compels one to think more positively about the distinction between mass and force than was necessary when x pounds or kilogrammes could refer to either. Kilogrammes are now a mass unit only. The seven SI base units are given.
Having prepared the mind for the conversion to the new system, recommendations on using the system are given based on publications by The National Physical Laboratory and the Standards Institution in Britain.
The selection of working units is given, and these are shown to give the calculator least trouble with factors and show the simplicity of the system. Worked examples on sheet, solids of revolutions and shells of revolutions are given, together with volumes in litres.
First moments and moments of inertia tabulations are then discussed, with regard to small and large configurations.
Tabulations and a graph which viii be of assistance in starting to estimate in SI units will be given, at present these are:
Sheet metals
Tube
Tabulation of mass densities
Tabulation showing the spectrum of material densities
Graph – Radius of ‘rations in squared/1000 units
The conclusion will show that the appropriate choice of working units it is possible to work easily within the SI framework. One such choice is given, and these unused to working with large numbers will soon have the ‘feel’ if they adopt fixed rules. The paper is based on three years work and seeks to encourage those about to work in SI units.