Peter can swim at a speed of 1.5 ms^-1 in still water. He needs to swim across a river. The river, flowing at a constant speed of 2 ms^-1, has parallel banks 180 m part. There is a water fall 210 m downstream from his starting point.
(a) If Peter swims at right angles to the current (see the figure), will he fall into the waterfall? Explain your answer.
(b) At what angle to the current should Peter swim so that he can reach the opposite bank safely and in the shortest possible time? Give your answer correct to the nearest degree.
