Question

A bird is flying `3m` above the surface of water,If the bird is diving vertically down with speed `=6m//s`his apparent velocity as seen by a stationary fish underwater is:
A. `8m//s`
B. `6m//s`
C. `12m//s`
D. `4m//s`

Answer 1

Correct Answer - A

distance of bird appeared to fish
`h=x+muy`
Differentiating w.x.t `rArr (dh)/(dt)=(dx)/(dt)+mu(dy)/(dt)rArr (dh)/(dt)=(4)/(3)xx6`
` (dh)/(dt)=8m//s`