# Net force on roof from wind? Using Bernoulli's eq?

• ronartest
In summary, the problem involves calculating the net force on a horizontal roof with an area of 300 m squared, given a wind speed of 24 m/s. The relevant equation is Bernoulli's equation, which can be simplified for a horizontal roof. After plugging in the numbers, the resulting total force on the roof is 111715.2 N/m squared. There may be a slight discrepancy in the answer due to rounding. The left side of the equation represents the wind blowing at 24 m/s, while the right side represents the air at rest.
ronartest

## Homework Statement

If wind blows at 24 m/s over your house, what is the net force on the roof if its area is 300 m squared?

## Homework Equations

Bernoulli's equation? P1+1/2pv1sqrd+pgy1=P2+1/2pv2sqrd+pgy2

## The Attempt at a Solution

Really didn't know where to go with this. I remembered my teacher mentioning that Bernoulli's equation was relevant. Tried plugging in the numbers, but didn't have any success. Any help would be extremely appreciated, as I have a final on this tomorrow morning. Thanks

In case of a horizontal roof, the terms containing the height y will cancel in Bernoulli's equation. The wind blows above the roof, the pressure is lower there than below the roof, in the building, where the air is in rest. If Po is the pressure of the air in rest, P+1/2 d v2=Po. The total force on the roof is (Po-P)A, (A is the area of the roof). You need the density of air (d). ehild

Thank you so much for your help.
from bernoulli's I get to .5(d)(v1sqrd)=P2-P1. Once I plug in my numbers: .5(1.293)(576)=372.384. Then multiplied by the area: 372.384(300)= 111715.2 N/msqrd. For some reason the study sheet has the answer as 108000 N/msqrd, but maybe this could just be rounding.
Conceptually, I'm wondering so on the left side of the equation is the wind blowing 24m/s, while on the right side it is stopped? Thank you so much, you have been monumentally helpful.

## 1. What is the net force on a roof from wind?

The net force on a roof from wind is the sum of all the individual forces acting on the roof due to the wind. This includes the pressure force, drag force, and lift force.

## 2. How is the net force on a roof from wind calculated?

The net force on a roof from wind can be calculated using Bernoulli's equation, which takes into account the air pressure and velocity at different points around the roof. This equation is based on the principle of conservation of energy.

## 3. What factors affect the net force on a roof from wind?

The net force on a roof from wind is affected by several factors, including the wind speed, the shape and size of the roof, the angle of the roof, and the surrounding terrain. These factors can change the air pressure and velocity around the roof, thus affecting the net force.

## 4. Can the net force on a roof from wind be negative?

Yes, the net force on a roof from wind can be negative if the wind direction and velocity are such that the pressure and lift forces are in the opposite direction of the drag force. This can happen if the wind is blowing upwards or if the roof has a unique shape that creates lift.

## 5. How can the net force on a roof from wind be minimized?

To minimize the net force on a roof from wind, the design of the roof can be optimized to reduce the pressure and lift forces. This can be achieved by using streamlined shapes, adding wind deflectors, or changing the angle of the roof. Proper maintenance and regular inspections can also help to minimize the effects of wind on a roof.

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