Q. Out of the two cars $A$ and $B$, car $A$ is moving towards east with a velocity of $10\, m / s$ whereas $B$ is moving towards north with a velocity $20\, m / s$, then velocity of $A$ w.r.t. $B$ is (nearly)
Motion in a Plane
Solution:
$\vec{V}_{A B}=\vec{V}_{A}-\vec{V}_{B}$
$V_{A B}=\sqrt{V_{A}^{2}+V_{B}^{2}}$
$\left|\vec{V}_{A B}\right|=\sqrt{10^{2}+20^{2}}$
$=\sqrt{100+400}=\sqrt{500} \simeq 22\, ms ^{-1}$
