Assertion : Particle A is moving eastwards and particle B...

Assertion is true: Let velocity of $A$ be ($\mathrm{v}$\_A=v $\mathrm{i}$) (eastwards) and velocity of $B$ be ($\mathrm{v}$\_B=v $\mathrm{j}$) (northwards), where $v$ is the speed. The velocity of $A$ with respect to $B$ is ($\mathrm{v}$\_A B=$\mathrm{v}$\_A-$\mathrm{v}$\_B=v $\mathrm{i}$) -vj . This vector has a positive x -component and a negative y -component, which corresponds to the south-east direction. Reason is false: Relative velocity is zero only if both the magnitude and direction of the velocities are the same. Here, only the magnitudes (speeds) are the same, but their directions are perpendicular (east vs. north). Therefore, their relative velocity is not zero.