1. Units and Dimensions
Conversion Factors
Length:
1 ft (feet) = 12 in (inch) = 0.3048 m
1 in = 2.54 cm
1 mile = 1.61 km
Area:
1 ft\(^2\) = 1 \(\times\) (0.3048 m)\(^2\) = 0.0929 m\(^2\)
1 hectare = \(100 \text{ m} \times 100 \text{ m}\) = 10,000 m\(^2\)
1 acre = \(66 \text{ ft} \times 660 \text{ ft}\) = 43560 ft\(^2\) = 0.4047 hectare
(66 ft = 1 chain; 660 ft = 1 furlong)
Cents and acres are SI units of measurement of land. 1 acre is equal to 100 cents.
Volume:
1 m\(^3\) = 1000 litre
1 litre = 1000 cm\(^3\) (cc; cubic centimeters) = 1000 milli litre (mL)
1 mL = 1 cm\(^3\)
Temperature:
= (\(\times\)9/5) + 32
1 rise = 1.8 rise
\(-40^\circ\text{C} = -40^\circ\text{F}\)
Human body temperature: 98.4= 36.9.
K (Kelvin) = 273 +
R (Rankine) = 460 +
Kelvin and Rankine are absolute temperature scales. i.e., there is no negative K or R values.
Force:
1 kg.m/s\(^2\) = 1 N
1 kg\(_f\) = 1 kg \(\times\) 9.812 m/s\(^2\) = 9.812 kg.m/s\(^2\) = 9.812 N
1 lb\(_f\) = 0.454 kg \(\times\) 9.812 m/s\(^2\) = 4.45 kg.m/s\(^2\) = 4.45 N
Energy:
1 cal = 4.184 J
About 2500 kcal/day ( 10 MJ/day) is the per capita food energy requirement of a human-being.
Power:
J/s = W
1 hp (horse power) = 746 W
Typical wind turbine’s power rating is 1 MW. The power rating of typical thermal power plant is 1000 MW.
1 ton of refrigeration = 50 kcal/min.
Pressure:
N/m\(^2\) = Pa (Pascal)
1 atm = \(1.01325 \times 10^5\) N/m\(^2\) = 1.01325 bar = 760 mm Hg