70 mph wind will cause 12.527 psf dynamic wind pressure. On a 100 sq. ft wall, this would mean a wind load of 1252.7 lbs. The following steps will help you verify this:
Multiply the air density by the square of the wind speed and 0.5:
dynamic pressure = 0.5⋅1.225 kg/m³⋅(70 mph)² = 0.5⋅1.225 kg/m³⋅(31.3 m/s)² = 599.8 Pa
Convert this into pounds per square foot (psf):
599.8 Pa⋅0.020885 psf/Pa = 12.527 psf
Multiply the dynamic pressure with the wall's effective surface area to obtain the wind load:
wind load = 12.527 psf⋅100 ft2 = 1252.7 lbs
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