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A fish rising up vertically toward the surface of water with speed `3ms^(-1)` observes a bird diving down vertically towards it with speed `9ms^(-1)` . The actual velocity of bird is

A

3.6 m/s

B

4.5 m/s

C

6.0 m/s

D

12.0 m/s

Text Solution

Verified by Experts

The correct Answer is:
B
(b) Fish is observer and bird is object.

Apparent distance between F and B at some instant will be,
y=(x+`mu`h)
`(-(dy)/(dt))=(-(dx)/(dt))+(mu)(-(dh)/(dt))`
`9=3+4/3(-(dh)/(dt))`
`therefore -(dh)/(dt)=4.5m/s`
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