A boat, propelled so as to travel with a speed of 0.5m/s in still water, moves across a river that is 60m wide. The river flows across with a speed of 0.3m/s.
(a) At what angle, relative to the straight-across direction, must the boat be pointed?
(b) How long does it take the boat to cross the river?
Drawing the velocity vectors, we have
(5cosθ)^2 + (0.3)^2 = 5^2
cosθ = 0.998
θ = 3.62°