Question

(13) A swimmer at point A on one side of river wants to
reach at a point B on the other side by swimming only.
Line AB makes angle 30° with the river flow. Velocity
of swimmer is equal to velocity of river flow in magni-
tude. In what direction o with the line AB should he
try to swim to reach at B.
1
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Answer 1

Answer: theta= 30 degrees

Explanation: tan alpha=

A sin theta / B + A sin theta

Now, tan 30 =

Vsr sin theta/ Vr + Vsr cos theta

1/root(3) = Vsr sin theta/ Vsr+ Vsr cos theta ( Vsr= Vr)

1/root 3 = sin theta/ 1+ cos theta

Tan theta/2 = tan 30

Theta = 60 degree

Beta= 60-30 = 30

Answer 2

Answer: 30°

Explanation:

Components of both velocities must be same along line of motion.

$v_r\cos \theta = v_r \cos 30° \\ \theta = 30°$

Hope it helps!! :P