A wind with speed 40 m/s blows parallel to the roof of a

A wind with speed 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m². Assuming that the pressure inside the house is atmosphere pressure, the force exterted by the wind on the roof and the direction of the force will be (ρ_air = 1.2 kg/m³)

1. 4.8 × 10⁵ N, upwards
2. 2.4 × 10⁵ N, upwards
3. 2.4 × 10⁵ N, downwards
4. 4.8 × 10⁵ N, downwards

According to Bernoulli’s theorem,

P +	1	ρv² = P₀ + 0
	2

So , ∆P =	1	ρv²
	2

F = ∆P =	1	ρv²A
	2

=	1	× 1.2 × 40 × 40 × 250
	2

= 2.4 × 10⁵ N (upwards)