How do I find the pressure difference?

Question

A hurricane wind blows across a 6.0 m by 16.5 m flat roof at a speed of 100 km/hr.

How do I find the pressure difference in Pa?

How do I find how much force is exerted on the roof, in N?

Answer 1

Force = Pressure x Area

Change in Pressure = (1/2 x Density of air x Velocity final) - (1/2 x density of air x Velocity initial)

Initial velocity equals 0, so Change in pressure equals 1/2*1.29*100^2 = 6450 Pa

----given that the density of air is equal to 1.29 kg/m^3

Force = Pressure*Area

Force = 6450*(6.0 * 16.5)

Force = 638550 N