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

Vw = 4.22 km/h[17.4o] S. of E. = 4.22km/h[ 355.8o] CCW.
Vs = 17.5km/h[90o] CCW.

Vr = 4.22[17.4o ]+ 17. 5[90o],
X = 4.22*Cos17.4 + 17.5*Cos90 = 4.03 km.
Y = 4.22*sin17.4 + 17.5*sin90 = 18.8 km.
Vr = 4.03 + 18.8i = 19.2 km[77.9o] CCW. = Resultant velocity of ship.