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PRACTICE · MEMBERSIntermediate · Single correct

PRACTICE / River crossing

Cross the river, then measure the drift.

A swimmer aims directly across a river of width 120 m and swims at 5 m/s relative to the water. The water flows downstream at 3 m/s relative to the bank.

How far downstream does the swimmer land?

Organize the givens & assumptions
  • Width: 120 m
  • Across-water component: 5 m/s
  • Downstream current: 3 m/s

The current is uniform and parallel to the banks. The swimmer maintains the stated heading and speed relative to the water.

  1. A24 m24\ \mathrm m
  2. B40 m40\ \mathrm m
  3. C72 m72\ \mathrm m
  4. D120 m120\ \mathrm m

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