Question

density (kg/m) viscosity (cp mPa s) VISCOsI water 20°C air 20°C 1000 1.204 1090 1.03 02217 250,000 eanut butter

Answer 1

(1) For the radius, we have

r = 2 (Area / Perimeter)

r = 2 [Area / (2$\pi$r)]

Area = $\pi$r²$\Leftrightarrow$ (1.5 m²) = (3.14) r²

r² = [(1.5 m²) / (3.14)]

r = _$\sqrt{}$0.4777 m²

r = 0.691 m

The Reynold's number which will be given by -

R = (2 r _$\rho$ v) / _$\eta$

where, _$\rho$ = density of an air = 1.204 kg/m³

v = speed of a car = 2 m/s

_$\eta$ = viscosity of an air = 0.02217 Pa.s

then, we get

R = [2 (0.691 m) (1.204 kg/m³) (2 m/s)] / (0.02217 Pa.s)

R = [(3.327856 kg/m.s) / (0.02217 kg/m.s)]

R = 150.1

(2) The Reynold's number which will be given by -

R = (2 r _$\rho$ v) / _$\eta$

where, _$\rho$ = density of an air = 1.204 kg/m³

v = speed of a car = 27 m/s

_$\eta$ = viscosity of an air = 0.02217 Pa.s

then, we get

R = [2 (0.691 m) (1.204 kg/m³) (27 m/s)] / (0.02217 Pa.s)

R = [(49.926056 kg/m.s) / (0.02217 kg/m.s)]

R = 2251.9