A stream-lined body falls through air from a height `h` on the surface of a liquid . Let `d` and `D` denote the densities of the materials of the body and the liquid respectively, if `D gt d`, then the time after which the body will be intantaneously at rest, is:

Options

A. `sqrt((2h)/(g))`
B. `sqrt((2h)/(g) . D/d)`
C. `sqrt((2h)/(g) . d/D)`
D. `sqrt((2h)/(g))((d)/(D-d))`

Answer

D

Explanation

Apparent weight = VDg-Vdg
`implies` Vda = VDg-Vdg
`a=((D-d)/(d))g" "rarr` Retardation
`v=sqrt(2gh)`
`implies` Time to rest `v/a=(sqrt(2gh) xx d)/((D-d)g), t=sqrt((2h)/(g))((d)/(D-d))`