A jet water, whose cros section is 'a' strikes a wall making an angle `theta` with normal and elastically rebounds. The velocity of water of density 'd' is v. Force exerted on wall is :-

Options

A. `2 av^(2) d cos theta`
B. ` 2 av^(2) d sin theta`
C. `2 av d cos theta`
D. av d `cos theta`

Answer

A

Explanation

`Deltap=2mv cos theta`
`F=(delp)/(delt)=(2v cos theta)(delm)/(delt)`

The mass crossing an area in t would be
`vxxtxxAxxdel=m`
`therefore (dm)/(dt)=v_(Ad)`
`therefore F=2av^(2)delcps theta`