Question

A river is flowing from west to east at a speed of 5m/min a man on the south bank of the river capable og swimming at 10m/min wants to swim across the river in the shortedt time he should swim in a direction

Answer 1

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)