A river flows east at 5 m min⁻¹. A swimmer from the south bank can swim at 10 m min⁻¹ in still water and wants minimum crossing time. His resultant ground velocity will be directed:
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Question

A river flows east at 5 m min⁻¹. A swimmer from the south bank can swim at 10 m min⁻¹ in still water and wants minimum crossing time. His resultant ground velocity will be directed:

G1 Physics · Accepted Answer

For minimum time he swims due north relative to water. Ground components are 5 east and 10 north, so the direction is tan⁻¹(10/5)=tan⁻¹2 north of east. Option B.