Problem statement In the not-so distant past, authorities recommended leaving the windows to a house open in a tornado to equalize the pressure and avoid blowing off the roof. We can estimate the validity of the advice. Assume the pressure inside the house is one atmosphere. Approximate Densities of roofing materials: Doug Fir 2x6: 1 kg/ft Plywood 5/8": 0.85 kg/ft^2 Gravel roofing 2.5: kg/ft^2 For a 40ft x 60f. area of roof, there are 40x20 ft of 2x6 (1.5 ft spacing between 2x6's) and 2400 ft^2 of plywood and gravel roofing. Assume 6 screws per 2x6 with a holding force of 500N each. Using the maximum pressure difference across the roof and the above data, can the roof blow off because of the pressure drop during a tornado, or is this not a valid concern? Relevant equations ##F=PA=\rho g h?## Work done so far Plywood and roofing: 40ft x 60ft = 12.192m x 18.288m = 731.52m^2 Joists: 40ft x 20ft = 12.192m x 6.096m = 243.84m^2 Screws: 6 screws x 40 joists = 240 x 500N = 120kN I’m afraid I do not know how to start this problem. It seems a little abstract from what we have already learned.