River width L = 300m, water velocity V1 = 3m / s, ship velocity V2 = 5m / s in still water River width L = 300m. Water velocity V1 = 3m / s. ship velocity V2 = 5m / s in still water. Find 1 to cross the river in the shortest time. Find 2 to cross the river in the shortest displacement. Find 3 to cross the river in the shortest displacement. When the bow of the ship is 37 degrees to the upstream bank, find the sailing time to reach the opposite bank

1. The shortest time t = L / V2 = 300 / 5 = 60s. 2. Because the ship's speed V2 > water speed V1, it can cross the river vertically. If there is v2cos θ = V1 (θ is the angle between the bow direction and the upstream bank), then cos θ = 0.6, t = L / v2sin θ = 300 / (5 * 0.8) = 75m

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