Tuesday

March 3, 2015

March 3, 2015

Posted by **Catie** on Monday, August 15, 2011 at 12:11am.

What is the pressure difference? Use 1.28 kg/m^3 for the density of air.

How much force is exerted on the roof?

If the roof cannot withstand this much force, will it "blow in" or "blow out"?

Help?

- Math -
**MathMate**, Monday, August 15, 2011 at 9:58amUse Bernoulli's equation:

P1+ρgh1+(1/2)ρv1² = P2+ρgh2+(1/2)ρv2²

where

P1=exterior pressure

P2=interior pressure

v1=exterior wind velocity

v2=interior wind velocity = 0

h1-h2 is the negligible height differences

ρ=density of air (1.293 kg-m^-3)

which by neglecting ρg(h2-h1), and substituting v1=0 we get

P2-P1=(1/2)ρv1²

v1=190km/h=52.778m/s

ρ=1.293kg/m³=12.7N/m³

Suction force (blows out):

=area*pressure difference

=6m*15m*(1/2)*1.293kg/m³*(52.8m/s)²

=162,073 N

The above calculation of pressure assumes:

1. the pressure factor is -1 (which is not far for a flat roof).

See:

(Broken Link Removed)

2. the STP value of ρ=1.293kg/m³ instead of 1.28 as stipulated. You will need to make adjustments to get the correct answer.

**Answer this Question**

**Related Questions**

Math - A hurricane wind blows across a 6.00 m times 15.0 m flat roof at a speed...

PHYSICS - HELP - A wind with speed 45 m/s blows across a roof 20 m long and 12 m...

physics - A 45 m/s (100 mph) wind blows across the top of a flat-roofed house. ...

Advanced Physics - If wind blows at a speed of 30 m/s over the roof of your ...

physics - (a)If the wind blows at 30m/s over the roof of your house, what is the...

physics - during a thunderstorm,wind with a speed of 47.7 m/s blows across a ...

physic - If wind blows at 34m/s over a house, what is the net force on the roof...

Physics - Matter - Wind blows around a skyscraper with a speed of 18 m/s outside...

Algebra - In a hurricane, the wind pressure varies directly as the square of the...

Physics - An airplane wing is designed so that the speed of the air across the ...