A wind with speed `40 m//s` 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 force will be : `(rho_(air)=1.2 kg//m^(3))`

Options

A. `4.8xx10^5` N, upwards
B. `2.4xx10^5` N. upwards
C. `2.4xx10^5` N, downwards
D. `4.8xx10^5` N, downwards

Answer

B

Explanation

From bernoulli.s equation-
`P+1/2 rho v^2=P_0+0`
`implies Delta P=1/2 rho v^2 implies F=1/2 rho v^2 A`
`implies F=1/2 xx 1.2 xx(40)^2 xx 250`
`=2.4xx10^5` N upwards