NEET2015PhysicsMechanical Properties of FluidsActual
A wind with speed 40   m   s - 1 blows parallel to the roof of a house. The area of the roof is 250   m 2 . Assuming that the pressure inside the house is atmospheric pressure, the force exerted by the wind on the roof and the direction of the direction of the force will be : ρ air   = 1 . 2   kg   m - 3  
Options
- A4.8 × 10 5 N, downwards
- B4.8 × 10 5 N, upwards
- C2.4 × 10 5 N, upwards
- D2.4 × 10 5 N, downwards
Correct answer
C. 2.4 × 10 5 N, upwards
Step-by-step solution
By Bernoulli's equation, P + 1 2 ρ v 2 = P 0 + 0 P 0 - P = 1 2 ρ v 2 F = 1 2 ρ v 2 A = 1 2 × 1.2 × 40 2 × 250 = 1 2 × 1.2 × 1600 × 250 = 2.4 × 10 5 N, upwards