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## Table of constants, conversions and other data

 Measure of distance 12 inches = 1 foot 3 feet = 1 yard 1760 yards = 1 mile 5,280 feet 1 inch = 2.54 cm 1 metre = 1.09 yards 1 metre = 39.4 inches 1 furlong = 220 yards 1 fathom = 6 feet 1 sea mile = 6080 feet 1 knot = 1 sea mile per second 1 Km = 0.621 miles conversion factor about 5 / 8 Measure of area 484 sq yds = 1 chain 10 chains = 1 acre 4840 sq yds;  possibly the area of land an ox could plough in one day 1 hectare = 10,000 sq metres a metric measurement of area 1 hectare = 2.47 acres 640 acres = 1 sq mile 100 hectares = 1 sq Km Measure of volume 1 litre = 1,000 cc cubic centimetres 1 litre = 100 cl centilitres; wine bottles hold 70 cl (about six glasses) 1 litre water  weighs 1 Kg 1 litre = 0.22 gallons 1.76 pints; to convert litres to gallons divide by 5 and add ten percent 1 litre = 1.76 pints 1 gallon = 277 cubic inches 1 gallon is defined as the volume of 10 lbs of water 1 cu ft = 6.24 gallons 1 dram = 1/8 fl oz 1 teaspoon About 5 ml.  Teaspoon's vary in size so always use a calibrated measuring spoon (eg from the chemist) for medicines, and cooking. 1 pint the volume of 20 fluid ounces of water; about 568 ml 2 pints = 1 quart 8 pints = 1 gallon 500 ml = 0.88 pint 500 ml is about ten percent short of one pint Measure of weight Avoirdupois 16 oz = 1 lb lb is shorthand for pound; oz = ounce 14 lb = 1 stone 112 lb = 1 cwt the weight of a sack of grain 20 cwt = 1 ton 2240 lb 1,000 grams = 1 Kg 1,000 Kg = 1 metric tonne 1 kg = 2.2 lb 1 lb = 454 grams 1 tonne = 0.984 ton one metric tonne is close to one imperial ton 1 lb = 7000 grains the grain was originally the weight of a barley seed 1 oz troy = 480 grains obsolete Constants Speed of light in vacuum 3 X 10E8 metres per second;  (10E8 = 100 million) Speed of sound in air 1,100 feet per second or about 750 mph or 340 metres per second Radial distance of lightning Divide time between flash and bang in seconds by five to give distance in miles pi 3.1416 or as a fraction about 22 / 7 1 radian 57 degrees approx;  (360 deg = 2pi radians) Base (e) used in natural logs 2.7183 Mean radius of earth 6,371 Km about Distance to the moon 384,400 Km about (centre to centre); one way delay about one second Distance to the sun 150 million Km about;  500 seconds at the speed of light Geosynchronous orbit 35,786 Km; two way delay about 0.25 second Distance to planet Mars 70 million Km approx; two way delay about ten minutes 1 Atmosphere (Bar) 760 mm column of mercury or a pressure of about 1 Kg per sq cm (about 15 psi) 60 mph = 88 feet per second 1 knot = 1.7 fps about 50 knots = 58 mph about Acceleration due to gravity 32.2 feet per second per second or 981 cm per sec per sec Specific gravity Water 1 Brass 8.5 about Copper 8 Glass 2.5 about Gold 19.3 Iron (wrought) 7.9 Lead 11.4 Mercury 13.6 Platinum 21.5 Silver 10.5 Alcohol 0.8 Methylated spirit 0.83 Petrol 0.7 Ice 0.917 Work and heat 1 Watt = 1 Joule per sec 10E7 ergs per sec 1 Horse Power (HP) 550 ft lbs per sec or about 746 watts 1 Kw 102 Kg metres per sec Coefficient of expansion Brass 1.9 X 10E-5 Copper 1.67 X 10E-5 Iron 1.1 X 10E-5 about;  extremes of temperature can cause railway track to buckle or fracture, so track must be designed to allow for this and be monitored. Radio Boltzmann's constant (k) 1.38 X 10E-23 Joules per deg K or equivalent radio noise power (kTB) minus 228.6 dbW per deg K per Hz bandwidth. Spare Disclaimer: this information is provided as a guide for retired people. All numbers are approximate and no liability is accepted for errors.