The stream of a river is flowing with a speed of 2 km h- 1 . A swimmer can swim at a speed of 4 km h- 1 . The direction of the swimmer with respect to the flow of the river, to cross the river straight, is

Question

The stream of a river is flowing with a speed of 2 km h- 1 . A swimmer can swim at a speed of 4 km h- 1 . The direction of the swimmer with respect to the flow of the river, to cross the river straight, is (A) 150°  (B) 90°  (C) 120°  (D) 60°

Tardigrade Admin · Accepted Answer

To reach the point directly opposite to the starting point, the resultant velocity of swimmer should be as shown in figure.
Solution

From figure

s in θ = \frac{2}{4} = \frac{1}{2}

θ = 3 0^{\circ}

Angle with flow

= 9 0^{\circ} + 3 0^{\circ} = 12 0^{\circ}

Q. The stream of a river is flowing with a speed of $2 km h^{- 1}$ . A swimmer can swim at a speed of $4 km h^{- 1}$ . The direction of the swimmer with respect to the flow of the river, to cross the river straight, is

$15 0^{\circ}$

$9 0^{\circ}$

$12 0^{\circ}$

$6 0^{\circ}$

To reach the point directly opposite to the starting point, the resultant velocity of swimmer should be as shown in figure.

From figure
$s in θ = \frac{2}{4} = \frac{1}{2}$
$θ = 3 0^{\circ}$
Angle with flow $= 9 0^{\circ} + 3 0^{\circ} = 12 0^{\circ}$

Q. The stream of a river is flowing with a speed of 2kmh−1 . A swimmer can swim at a speed of 4kmh−1 . The direction of the swimmer with respect to the flow of the river, to cross the river straight, is

150∘

90∘

120∘

60∘