a person aiming to reach the exactly opposite point on the bank of a stream is swimming with a speed of 0.5 m/s.at an angle of 120 degree with the direction of flow of water. find the speed of water in the stream.................

Here, V_r is the velocity of the river w.r.t ground, V_m is the velocity of the man w.r.t river and V is the velocity of the man wrt ground.

tan (90) = [V_m sin120]/[V_r + V_mcos120]

Therefore,

V_r + V_mcos120 = 0

=> V_r = - V_mcos120 = -(0.5)(-0.5) = 0.25 m/s

Thus, velocity of river is 0.25 m/s wrt the ground.