Kinematics 2
A river is flowing from west to east at a speed of 5 m/min. A man on the south bank of the river, capable of swimming at 10 m/min in still water, wants to swim across the river in the shortest time. He should swim in direction .
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1 solution
The man's east-west motion is independent of his north-south motion (sort of like how horizontal and vertical motion are independent in projectile motion). He will end up downstream of where he started, just like how a projectile fired horizontally will fall; however, the best way for him to "maximize" his velocity to the north is to swim north, just like how firing a projectile directly horizontally will maximize its horizontal velocity.