Measure of distance |
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12 inches = 1 foot |
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3 feet = 1 yard |
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1760 yards = 1 mile |
5,280 feet |
1 inch = 2.54 cm |
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1 metre = 1.09 yards |
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1 metre = 39.4 inches |
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1 furlong = 220 yards |
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1 fathom = 6 feet |
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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 |
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484 sq yds = 1 chain |
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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 |
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640 acres = 1 sq mile |
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100 hectares = 1 sq Km |
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Measure of volume |
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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 |
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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 |
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1 gallon = 277 cubic inches |
1 gallon is defined as the volume of 10 lbs of water |
1 cu ft = 6.24 gallons |
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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 |
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1,000 Kg = 1 metric tonne |
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1 kg = 2.2 lb |
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1 lb = 454 grams |
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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 |
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Disclaimer: this information is provided as a guide for retired people. All numbers are approximate and no liability is accepted for errors.
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