Fluids Approximations/Memorization

0 < b << 1, (1+b)^A = ?

1+Ab

temperature of air at STP

300 K

pressure of air at STP

1 × 10^5 kg/m³

density of air at STP

1 kg/m³

density of wood, plastic, and most liquids at STP

1000 kg/m³

density of metal

5000 kg/m³

viscosity of air at STP

2 × 10^−5 Pa*s

viscosity of water at STP

1 × 10^−3 Pa*s

viscosity of engine oil at STP

200 × 10^−3 Pa*s

gas constant of air at STP

300 J/(kg*K)

specific heat ratio of air at STP

1.4 or 7/5

pressure (Pa to psi)

1 × 10^5 Pa ≃ 15 psi

pressure (Pa to bar)

1 × 10^5 Pa = 1 bar

volume (m³ to gallon)

1 m³ ≃ 250 gallon

volume (m³ to L)

1 m³ = 1000 L

length (m to ft)

1 m ≃ 3 ft

length (km to mile)

1 km ≃ 1.6 mile

speed (m/s to mph)

1 mph ≃ 0.5 m/s

force (N to lb)

4 N ≃ 1 lb

power (W to hp)

750 W ≃ 1 hp

area of square of length b

b²

area of rectangle with lengths a and b

ab

area of triangle with base 𝑏 and height ℎ

1/2*b*h

area of circle with radius 𝑟 and diameter d

𝜋r²; 𝜋d²/4

surface area of sphere with radius 𝑟

4𝜋r²

perimeter of circle with radius 𝑟 and diameter d

2𝜋𝑟; 𝜋d

volume of cube of length b

b³

volume of cuboid with lengths 𝑎, 𝑏, c

abc

volume of cylinder with radius 𝑟 and height ℎ

𝜋r²ℎ

volume of cone with radius 𝑟 and height ℎ

𝜋/3 * r² * ℎ