(a) A flat roof is very susceptible to wind damage during a thunderstorm and/or
ID: 1420636 • Letter: #
Question
(a) A flat roof is very susceptible to wind damage during a thunderstorm and/or tornado. If a flat roof has an area of 520 m2 and winds of speed 41.0 m/s blow across it, determine the magnitude of the force exerted on the roof. The density of air is 1.29 kg/m3.N
(b) As a result of the wind, the force exerted on the roof is which of the following?
downwardupward (a) A flat roof is very susceptible to wind damage during a thunderstorm and/or tornado. If a flat roof has an area of 520 m2 and winds of speed 41.0 m/s blow across it, determine the magnitude of the force exerted on the roof. The density of air is 1.29 kg/m3.
N
(b) As a result of the wind, the force exerted on the roof is which of the following?
downwardupward downwardupward
Explanation / Answer
given data
v1 = 0 m/s (at below the roof)
v2 = 41 m/s (at top of the roof)
Let P1 and P2 are the pressures at lower and upper surfaces of the roof
Use, Bernoulli's theorem,
P1 + 0.5*rho*v1^2 = P2 + 0.5*eho*v2^2
P1 - P2 = 0.5*rho*(v2^2 - v1^2)
= 0.5*1.29*(41^2 - 0^2) (here, rho
= 1084.2 pa
the net upward force of air on the roof, F = (P1 - P2)*A
= 1084.2*520
= 563784 N <<<<<<<<--------------Answer
b) Upward <<<<<<<<--------------Answer
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