A wind with speed `40m//s` blows parallel to the roof of a house .The area of the roof is `250m^(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)=1.2kg//m^(3))`

Options

A. `4.8xx10^(5)N`, downward
B. `4.8xx10^(5)N`, upward
C. `2.4xx10^(5)`N, upward
D. `2.4xx10^(5)N`, downward

Answer

c

Explanation

`2.4xx10^(5)N`, upward From Bernoulli.s equation,
`P+(1)/(2)rhov^(2)=P_(o)+o " " [becausev_("in")=o]`
`therefore(1)/(2)rhov^(2)=P_(o)-P " " [becauseP=(F)/(A)]`
`F=(P_(o)-P)A`
`thereforeF=(1)/(2)rhov^(2)A`

`=(1)/(2)xx1.2xx(40)^(2)xx250`
`=0.6xx1600xx250`
`240000`
`=2.4xx10^(5)N`, upward