AIPMT | 2015Basic Maths and Units and DimensionsHard

Question

A wind with speed 40 m/s blows parallel to the roof of a house. The area of the roof is 250 m2. Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the force will be :
(ρair = 1.2 kg/m3)

Options

A.4.8 × 105 N, upwards
B.2.4 × 105 N, upwards
C.2.4 × 105 N, downwards
D.4.8 × 105 N, downwards

Solution

    
By Bernaulli′s equation
P + ρv2 = P0 + 0
P0 - P = ρv2
F = ρv2A
F = 2.4 × 105 upward
Hence Option (2)

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