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A river 4.0 miles wide is following at t...

A river 4.0 miles wide is following at the rate of 2 miles/hr. The minimum time taken by a boat to cross the river with a speed v=4 miles/hr (in still water) is approximately

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The correct Answer is:
B
`tan alpha=v^(2)/Rxx1/(dv//dt)=(a^(2)s)/(Rav//2sqrt(s))=(2s)/R`
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ALLEN -MOTION IN A PALNE-EXERCISE-02
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