Question

A ship moves along the equator to the east with a speed 30 km/h. Southeastern wind blows 60^o to the east with 15 kmh^-1. Find the wind velocity relative to the ship.

• A. 39.7 kmh^-1, tan^-11/5 N of W
• B. 23.7 kmh^-1, tan^-11/3 N of W
• C. 37.5 klmh^-1, tan^-1 1/5 N of E
• D. None of these

Answer 1

Answer: (A)

39.7 kmh^-1, tan^-11/5 N of W

Answer 2

v_ws = v_w – v_s

= (15 cos 60$\widehat{i}$ + 15 sin 60$\widehat{j}$) – 30 $\widehat{i}$

|v|= $\sqrt{(39.5)^{2} + (7.5)^{2}}$ = 39.7 kmh^-1

tan β = 7.5/37.8 = 1/5

β = tan^-1 1/5 North of West.