Question

The stream of a river is flowing with the speed of 2 km per hour a swimer can swim at the speed of 4 km per hour what should be the direction of the swimmer with respect to the flow of river to cross the river straight

Answer 1

Answer:

At an angle of  120° with the velocity of the river.

Explanation:

LET:

Velocity of River be R

Velocity of Swimmer be S

Angle made by S with respect to R be θ

Angle made by Resultant with R be α

GIVEN

R=2km/hr

S=4km/hr

θ=?

α=90°

We know that,

tan α  =  Ssinθ/(R+Scosθ) = tan90°

⇒R+Scosθ=0

⇒cos θ = -R/S = -2/4 = -1/2 = cos120°

∴θ =120°

Answer 2

Answer:

the correct answer of the question is 120°