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A river is flowing at the rate of 6 km/h...

A river is flowing at the rate of 6 km/hr. A swimmer swims across with a velocity of 9 km/hr w.r.t. water. The resultant velocity of the man will be in (km/hr):-

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`s=ut+1/2 at^(2) rArr a=(u sin theta) t-1/2 g t^(2)`

`rArr t=(u sin theta +-sqrt(u^(2) sin^(2)theta-2ag))/g`
`Deltat=(2sqrt(u^(2) sin^(2) theta-2ag))/g`
For horizontal motion : `2a=u cos theta xx Deltat`
`rArr 2a=(u cos thetaxx2sqrt(u^(2) sin^(2) theta-2ag))/grArr theta=60^(@)`
`:. Deltat=(2a)/(u cos theta)=(2a)/(2sqrt(ag)xx1/2)=2sqrt(a/g)`
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