Question

A man walks westward on a ship with a speed of 4km/hr. The ship's propeller drives it 15km/hr south. What is the actual speed of the man relative to the Earth? What is the direction of his velocity?

Answer 1

The actual speed is

$$v=\sqrt{4^2+15^2}=15.52\text{ km/h}.$$

The direction is

$$\theta=\tan^{-1}\frac{15}{4}=75°\text{ S of E}.$$