Question

A man swims from a point A on bank of a river of width 100m.When he swims perpendicular to water current he reaches other bank 50m downstream.The angle to the bank at which he should swim to reache the directly opposite point b on another bank is

Answer 1

Answer:

120°

Explanation:

A man swims from a point A on bank of a river of width 100m.When he swims perpendicular to water current he reaches other bank 50m downstream.The angle to the bank at which he should swim to reache the directly opposite point b on another bank is

Let say Velocity of Man = V m/s

Velocity of Stream = S m/s

Let say he crossed river in T sec

then Vertical Distance (width) = VT  = 100

Horizontal Distance = ST = 50

=> V/S = 2

=> V = 2S

Let say Man Swim at angle of α  to the stream

Then Horizontal Velocity = VCosα = 2SCosα

Man Horizontal Velocity should cancel out Stream velocity so that he reaches directly opposite

=> 2SCosα + S = 0

=> Cosα = -1/2

=> α = 120°

Man should swim at an angle of 120° to the stream