Hurricane wind blowing across a flat roof

[xKalax]

1.A hurricane wind blows across a 7.8 m x 12 m flat roof at a speed of 180 km/hr.

What is the pressure difference?

How much force is exerted on the roof?
2. Homework Equations

P= p_atmos + pgd
P=F/A

The Attempt at a Solution

p = 101300Pa - (1.3)(9.8m/s^2)(93.6m^2)
p = 100107.5Pa

100107.5Pa = F/(93.6m^2)^2
F = 8.8 * 10^8 N

I know this is wrong, how do I go about solving this problem?

 

[jix]

That's not the right equation. Rather, it's not the entire equation.

First of all, the numbers you used don't even turn out to have the right units. As in, d = 93.6 m^2 doesn't have the right units for d.

And think about it, the speed is given for a reason. Get the full equation, and plug in the values, and easily get the answer.

 

[xKalax]

ok, I got the change in pressure to be 1625 Pa, which is correct.

I plug that into F = pA and get F = 1625Pa * 93.6m^2 = 152100, this seems too big.

I got it right, thank you!