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A man wishes to swim across a river 0.5k...

A man wishes to swim across a river 0.5km. wide if he can swim at the rate of 2 km/h. in still water and the river flows at the rate of 1km/h. The angle (w.r.t. the flow of the river) along which he should swin so as to reach a point exactly oppposite his starting point, should be:-

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The correct Answer is:
3
Kinetic energy of a projectile at the highest point `=E cos^(2) (theta)` where E is the kinetic energy of projection, `theta` is the angle of projection.
`E_("highest point")=E(cos 45^(@))^(2)=E(1/sqrt(2))^(2)=E/2`
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