Question

A river is flowing from west to east at a speed of 5 meters/minute. A man on the south bank of the 10 m/ min in still river, capable of swimming at water, wants to swim across the river in shortest time. He should swim in

Answer 1

Answer:

Due north.

Explanation:

Refer to the attached image to better understand the case.

Given;-        

                      Vr = 5 m/min (W⇒E)

                      Vm = 10 m/min ( Stationary, refer to the below dot)

Let, another dot opposite to Vm's dot represent the target to be reached which is due north. Also, let the time be Tmin. Now;-

Since,  

                        Tmin = D(width of the river)/ Vm   [which in this case, Vr is independent of Tmin]

So,

                        Tmin = D/Vm

                        D/Tmin = Vm  [which is due north]

Therefore, the man should swim due north.