If wind blows at 44 m/s over a house, what is the net force on the roof if its area is 180 m^2 and is flat?
physics - bobpursley, Sunday, November 15, 2009 at 8:28pm
Net force in which direction? There are two forces here, the force upward due to The Bernoulli effect(there is zero velocity below the roof), and wind shear force trying to blow the roof away. Most of the shear is due to the area normal to the wind.
It is not a problem most teachers would try to reduce to a simple calculation.
physics - drwls, Sunday, November 15, 2009 at 8:31pm
It is approximately
(1/2)*(air density)*V^2*(roof area), but depends upon what the pressure inside the house is, and that depends upon which windows or doors are open.
Air density is about 1.2 kg/m^3.
I get about 209,000N or 46,000 lb.
physics - bobpursley, Sunday, November 15, 2009 at 8:31pm
If this is a flat roof, approximate the force with Bernoulli alone.