Question

A wind with speed 45 m/s blows across a roof 20 m long and 12 m wide. The pressure inside the room is 1 atm. What is the net force on this roof due to the pressure difference inside and outside the roof? (The density of air is equal to 1.3 kg/m3.)

Question 1 options:
A) 2.4 x107 N

B) 6.3 x 105 N

C) 3.2 x 105 N

D) 7.0 x 103 N

E)
3.2 x 108 N

Answer 1

Use the Bernoulli equation for the pressure difference. Multiply that by the roof area.

net force = (roof area)*(1/2)(density)*V^2