Question

Daisy is running 5 m/s due East while crossing with Joel who is running 4 m/s due North. What is Daisy's actual velocity and angle relative to Joel's?

Answer 1

The relative velocity of Daisy with respect to Joel

$$v_{DJ}=\sqrt{v_D^2+v_J^2}=\sqrt{5^2+4^2}=6.4\:\rm m/s$$

The angle

$$\theta=\tan ^{-1}\frac{v_J}{v_D}=\tan ^{-1}\frac{5}{4}=51^{\circ}\; \rm S\;of\; E$$