A fish rising vertically up towards the surface of waterwith speed 3ms^(-1) observes a bird diving vertically down towards it with speed 9ms^(-1) The actual velocity of bird is (Given mu_ water =4/3

Options

A. 4.5 `ms^(-1)`
B. 5 `ms^(-1)`
C. 3.0`ms^(-1)`
D. 3.4 `ms^(-1)`

Answer

A

Explanation

Optical distance between fish and the bird is s = y. + ny
`(ds)/(dt) = (dy.)/(dt) + n(dy)/(dt)`
`rArr " " 9 = 3 + (4)/(3) xx (dy)/(dt) rArr (dy)/(dt) = 4.66 `m/s = 4.5 m/s.