A student wants to swim across a river of 100 m, the current is 1 m/s. He wants to swim the fast as possible. Another wants to swim the fast as possible and avoid a waterfall at the end of the river ( 10 to the end of the river). If they both use 2 m/s speeds when swimming, how fast do they go? And for the one avoiding a waterfall at what angle should he aim at?? I don't understand this, thanks in advance....
Answers (1)
The person who tries to avoid the waterfall has has the speed 2m/s. if the waterfall is at the left side, he definitely aim for the right side. Vertically, he needs to swim 100 meters. So, the time is 100/(2sin(x)), where x is the angle. Horizontally, he needs to avoid waterfall. So, the time is more than 10/(2cos(x)-1). The equation is 100/(2sin(x))=10/(2cos(x)-1). Solve it, we get the angle approximately equals to 54.45 degree.