
It is necessary to measure two or more quantities in the same units whenever we compare them. Comparing these units is only possible when one knows their introductory conversion rates. To understand better, let us take an example. A child cannot figure out how many kilograms of a commodity his mother asked him to bring from the market. However, he can figure out the quantity in litres because the packet has the quantity printed in litres. That is where unit conversions become necessary. One can easily convert a unit no matter how big the units are. Remember a basic rule of conversion from this example-
We know, 1 light year is equal to 0.946 x 1016 metres. Also, 1 mile is equal to 1.609 kilometres. And, 1 kms is equal to 1000m. Therefore, cancelling all the terms in the equation, 1 light year x 0.946 X 1016m1 light year x 1 km1000 m x 1 mile 1.609 km we get, 0.587x1013 miles.
|
kilo |
hecto |
deca |
metre/litre/gram |
deci |
centi |
mili |
|
1000 |
100 |
10 |
1 |
0.1 |
0.01 |
0.001 |
|
Volume units |
1 gallon |
3.785 litres |
|
1 cubic foot |
28.316 litres |
|
|
1 foot |
12 inches |
|
|
1 inch |
2.54 cms |
|
|
Length units |
1 Angstrom |
10-10m |
|
1 light year |
0.946 x 1016m |
|
|
1 mile |
1.609kms |
|
|
1 fermi |
10-15m |
|
|
Mass units |
1 pound |
453.592 grams |
|
1 ounce |
28.349 grams |
|
Time conversions |
|
|
1 min |
60 seconds |
|
1 hour |
60 min |
|
1 day |
24 hours |
|
1 week |
7 days |
|
1 year |
365/366 (leap year) days |
|
Energy conversions |
|
|
1 BTU (British thermal unit) |
1055 Joule |
|
1 erg |
1×10−7 Joule |
|
1 foot-pound |
1.356 Joule |
|
1 calorie |
4.186 Joule |
|
1 kilowatt-hour |
3.6×106 Joule |
|
1 electron volt |
1.602×10−19 Joule |
|
1 litre atmosphere |
101.13 Joule |
|
Area conversions |
|
|
1 sq. inch |
6.4516 x 10-4 square meter |
|
1 sq. foot |
9.2903 x 10-2 square meter |
|
1 acre |
4.0468 x 103 square meter |
|
1 hectare |
1 x 104 square meter |
|
1 sq. mile |
2.5888 x 106 square meter |
|
1 barn |
1 x 10-28 square meter |
|
Power conversions |
|
|
1 erg/sec |
1 x 10-5 watt |
|
1 BTU/hr |
0.2930 watt |
|
1 foot-pound/ sec |
1.356 watt |
|
1 horsepower |
745.7 watt |
|
1 calorie/ sec |
4.186 watt |
|
Pressure conversions |
|
|
1 atm |
101.3 kPa |
|
1 atm |
760mm Hg |
|
1 bar |
105 Pa |
|
1 psi |
68.948 mbar |
|
Temperature |
|
|
°F |
9/5 °C + 32 |
|
°C |
5/9 (°F – 32) |
|
K |
°C+273.15 |
|
K |
5/9(°F-32) + 273 |
1. Keep a factor of 1 for doing long-chain conversions. It will keep the conversions intact and straightforward.
2. Be careful while converting bigger chain units. Keep the actual numbers in proper places of numerators and denominators.
3. Do proper canceling of units from top to bottom or vice versa. Keep it clean and straightforward.
4. Accuracy is more important than speed. Be accurate while performing calculations. Speed will come after that.
5. Memorize the basic conversions thoroughly to avoid mistakes.
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