# Units¶

Memorize the following unit conversions:

• 3.28084 ft per m
• 2.20462 lbm per kg
• 32.174 lbm*ft/s$^2$ per lbf
• This is from $F = ma$
• 1055.056 J per Btu
• 25037 lbm*ft$^2$/s$^2$ per Btu
• 4.184 J per cal
• 101325 Pa per atm
• 0$^o$C = 273.15 K
• 0$^o$F = 459.67$^o$R
• 1$^o$C = 9/5$^o$F
• $^o$C = ($^o$F - 32)*5/9
• $^o$F = $^o$C*9/5 + 32

Also, remember these:

• 5280 ft per mile
• 12 in per foot
• 60 s per min
• 3600 s per hr
• 0$^o$C = 32$^o$F
• 1 cal is the energy to raise 1 g 1$^o$C (or K)
• 1 Btu is the energy to raise 1 lbm 1$^o$F (or R)

Memorize these constants:

• g
• 9.80665 m/s$^2$
• 32.174 ft/s$^2$
• R$_{gas}$
• 8314.46 J/kmol*K
• 1985.88 cal/kmol*K
• 1.98588 Btu/lbmol*R
• 10.73157 ft$^3$*psi/R*lbmol
• 49720 lbm*ft$^2$/s$^2$*R*lbmol
• Na
• 6.02214E26 (#/kmol)

Memorize these unit equivalences (written for SI, but similar for English units).

• N = kg*m/s$^2$
• Pa = kg/m*s$^2$
• J = kg*m$^2$/s$^2$
• density = kg/m$^3$
• viscosity = kg/m*s
• kinematic viscosity, thermal diffusivity, mass diffusivity = m$^2$/s

Memorize these properties

• Liquid water at 20$^o$C (68$^o$F) and 1 atm:
• density = 998 kg/m$^3$ = 62.3 lbm/ft$^3$
• Or 1000 kg/m$^3$
• viscosity = 1.002E-3 kg/m*s
• Or 0.001 kg/m*s
• Air at 20$^o$C (68$^o$F) and 1 atm:
• density = 1.204 kg/m$^3$ = 0.07518 lbm/ft$^3$.
• O(1)
• viscosity = 1.825E-5 kg/m*s
• O(1E-5)
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