1. Tardigrade
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  3. Physics
  4. A river 4.0 miles wide is flowing 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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Q. A river $4.0$ miles wide is flowing 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

Motion in a Straight Line

Solution:

Minimum time is taken when the boat crosses the river at right angles to its flow. The resultant velocity of boat and river should be at right angles to flow of river.
$t_{\min }=\frac{D}{v}=\frac{4}{4}=1 hr$