At the entrance channel of a harbor, the tidal current has a velocity of 4.22 km/hr in a direction 17.4o south of east. Suppose a ship caught in this current has a speed of 17.5 km/hr relative to the water. If the helmsman keeps the bow of the ship aimed north, what will be the speed of the ship relative to the ground?

1 answer

speed N = 17.5 - 4.22 sin 17.4
speed E = 4.22 cos 17.4
magnitude of speed = sqrt(N^2+E^2)
direction = tan^-1 (E/N) in true compass degrees (east of north)