Question

A river flowing west to east at speed 5m/min. A man on the south bank of the river, capable of swimming at 6m/min in still water, wants to swim across the river following the shortest path, then he should swim in a direction:

Answer 1

Explanation:

River = 5m/min V man = 10 m/minsuppose width of river is x mtsCase 1if he travels due norththen his resultant velocty ( due to velocity of downstream of water) acts 30 north of east and the distane to be covered to reach the other bank increses to = x/cos 30i.e., 2x /31/2 and resultant velocity is 11.2 m/minso time taken is x / 9.7 minsCase 2if he travels due 30 north of eastthen his resultant velocty ( due to velocity of downstream of water) actsdue north and the distane to be covered to reach the other bank will be x mts and resultant velocity is 8.7 m/minso time taken is x / 8.7 minsSo case 1 takes least timehe should travel due North(a)