Question

A 180-km/h wind blowing over the flat roof of a house causes the roof to lift off the house.

If the house is 5.0 m × 11.4 m in size, estimate the weight of the roof. Assume the roof is not nailed down.

Answer 1

The speed of the wind is v = 180km/h = (180) * (1000/3600) =50 m/s

The area of the house is A = 5.0 * 11.4 = 57.0m²

The pressure of the wind is

P = (1/2) * ? * v²

Here,? is the density of air and is equal to 0.001225*10³ kg/m³ = 1.225 kg/m^3

or P = (1/2) * 1.225* (50)^2  = 1531.25 N/m²

We know from the relation

P = (F/A)

Here,F is the force on the roof and A is the area of theroof.

or F = P * A = 1531.25* 80.0 = 122500 N

Therefore,the weight of the roof is w = 122500 N

I hope help you.....