Q89 / 180 · NEET 2019 (All India) · Physics

The speed of a swimmer in still water is 20 m s-1. The speed of river water is 10 m s-1 and is flowing due east. If he is standing on the south bank and wishes to cross the river along the shortest path, the angle at which he should make his strokes with respect to the north is given by

  • Correct answer
    A
    30° west
  • B
    0°
  • C
    60° west
  • D
    45° west

Solution

Figure

For reaching just apposite  bank of the river the net velocity at  the river should be  zero that means

vsinθ = velocity of river

sinθ=velocity of rivervelocity of swimmer

sinθ=1020=12
θ=30°
30° west of north

Hence, the correct answer is option: 'A'.

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