Question

 A boatman wants to take his boat to a point just opposite on the other bank of the river,then he will row-​

Answer 1

Answer:

Let v be the speed of boatman in still water.

Resultant of v and u

should be along AB. Components of

v

b

(absolute velocity of boatman ) along x and y-direction are,

v

x

=u−vsinθ

and v

y

=vcosθ

Further, tan45

∘

=

v

x

v

y

or 1=

u−vsinθ

vcosθ

∴v=

sinθ+cosθ

u

=

2

sin(θ+45

∘

)

u

v is minimum at, θ+45

∘

=90

∘

or θ+45

∘

and v

min

=

2

u