The downstream drifts of a swimmer crossing a river at equal angular deviations towards downstream and upstream are in the ratio 2:1. The ratio of swimmer speed to current speed cannot be less than:
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Question

The downstream drifts of a swimmer crossing a river at equal angular deviations towards downstream and upstream are in the ratio 2:1. The ratio of swimmer speed to current speed cannot be less than:

G1 Physics · Accepted Answer

Applying the drift expressions for equal angular deviations on opposite sides and imposing the 2:1 ratio gives the limiting ratio 1/3. Hence option A.