Question

A man can swim in still water at a speed of 6 kmph
and he has to cross the river and reach just opposite
point on the other bank. If the river is flowing at a
speed of 3 kmph, and the width of the river is 2 km.
the time taken to cross the river is (in hours)​

Answer 1

Answer:

If he swims 6 kmh^-1 .to a inclined to vertical In river plane.

then River is going through 3 kmh^-1

Which makes a obtuse triangle now

if the Result of them is go through the Perpendicular Line to the Horizontal.

then he can swim in the lowest time.

then

6 sin a=3

6 cos a= Result

sin a=0.5

then cos a=(root(3)/2)

so Result is 3 root(3)

now use S=ut

then 2=3root(3)×t

Because of that

t=2/3 root(3) seconds

Explanation:

use Vectors as Velocities