Question

The speed of air is 54km/hr above the roof of a house of area 60 sqm. Find the aerodynamic lift on the roof if the density of the air is 1.3kg/m'.
​

Answer 1

{let density =¥}

outside the house total energy of air flow per unit volume

=1/2 ¥v²+¥gh= constant.

from law of conservation of energy ,total energy of air inside and outside home is same.

by solving u will get that h1=h2

so eqn reduced to =1/2¥v²

Now the speed of air blow =54km/hr

=15m/s

as u know pressure difference (p2 -p1)=

=1/2¥v²

=1/2 *1.3*15²

=146.25N/m = 146 N/m(approx.)

lift on the roof = pressure difference* areaof the house.

=P2 -P1 *A

=146*60

=8760 N