- Home
- Standard 11
- Physics
9-1.Fluid Mechanics
normal
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 $(\rho _{air} = 1.2\,kg/m^3)$
A
$4.8 \times 10^5\,N,$ upwards
B
$2.4 \times 10^5\,N,$ upwards
C
$2.4 \times 10^5\,N,$ downwards
D
$4.8 \times 10^5\,N,$ downwards
Solution
$F=\Delta P \times$ Area
$\Rightarrow F=\left(\frac{1}{2} \rho \mathrm{V}^{2}\right) \times \mathrm{A}$
$\Rightarrow F=\frac{1}{2} \times 1.2 \times(40)^{2} \times 250$
$\Rightarrow F=2.4 \times 10^{5} \mathrm{N}$
Force will be upwards as pressure outside is low.
Standard 11
Physics
