[ Every Engineer Must Learn By Heart ]
The Metric System:
A system of weights and measures which was first adopted by France and is now almost universally used in the sciences and arts. The greater part of the population of the world works on the metric system. The metric is so called because it uses the “meter” as the primary unit.
The SI System of Units:
The International System of units abbreviated as “SI”. From French the SI is accepted in United States and throughout the world. It is a modern version of Metric System of units by the international agreement.
The SI units within the time replaced other systems.
U.S Customary Units:
The U.S customary or British System of Units also called the Foot Pound Second System (FPS) System has been the common system in English speaking countries, although the system within time be replaced by the SI Units (Best for many Years).
Engineers must be able to work in both the SI Units and FPS System of Units.
Basic Quantities and Units:
|Quantity||Dimensions||SI Units||FPS Units|
|Force||F||Newton (N)||Pound (lb)|
The standard relationship between English measures and Metric measures is as follows;
1 inch = 25.4 millimeters = 2.54cm
1 meter = 39.37 inches =1.09 yards
1 liter = 0.22 galls (imp.)
1 gallon (imp.) = 4.546 liters
1 gallon (US) = 3.785 liters
1 Kilogram (kg) = 2.2046 pounds (lb)
Metric Units of Weights/Mass:
1 tonne = 1,000,000 grams = 1000 kilograms
1 quintal = 100,000 grams = 100 kilograms
1 Slug = 14.606 kg
1 Slug = 32.2 lb
*The gram is the weight of one cubic centimeter or one millimeter of water.
*Kilogram is the weight of one liter of water.
*Tonne is the weight of one cubic meter of water.
Measures of Length:
Following are the basic measures of length in British Units;
12 inches = 1 foot
3 feet = 1 yard
220 yards = 1 furlong
8 fulongs = 1 mile
The measures of lengths in Metric Units are as follows;
1 Kilometer (Km) = 1000 meters
1 meter (m) = 100 centimeters (cm)
1 cm = 10 millimeter (mm)
Metric Units of Liquid Measures:
1 liter = 1000ml
1 liter = 1kg
1 kiloliter (1000 liters) = 1 cu. Meter
1 cu. ft. = 28.317 liters
1 cu. ft. = 0.028 cu. meters
1 cu. ft. = 6.24 galls (imperial)
1 cu. ft. = 7.48 galls (US)
1 imp. gall = 1.20 galls (US), liquid
1 imp. gall = 1.03 galls (US), dry
Indian/Pakistani Measures of Small Weights:
8 ratties = 1 masha
12 mashas = 1 tola = wt.of rupee coin (silver)
5 tolas = 1 chhatak
4 chhataks = 1 pau = 20 tolas
4 pau = 1seer = 80 tolas
10 seers = 1 maund
* 1 masha = 1 gram (approx.)
Measures of Area in Pakistan:
1 Acre = 43560 sq. ft
1 Acre = 4046.46 sq. m
1 Acre = 8 Kanals
1 Kanal = 20 Marlas
1 Marla = 225 sq. ft (* in some regions 272 sq. ft)
1 Marla = 15.50 sq. m
Miscellaneous Conversions Factors:
1 cu.m = 35.32 cu.ft.
1 Pound = 4.448 Newton (Force)
1 klb = 4.448 kN
1 Psi (lb/sq.in) = 6.689 Pascal (N/sq.m)
1 (lb/sq. ft) = 0.048 (kN/sq.m)
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