Two particles A, B are moving on two concentric circles of radii R₁ and R₂ with equal angular speed $\omega$ . At t = 0, their positions and direction of motion are shown in the figure : The relative velocity ${\overrightarrow{\mathrm{\upsilon }}}_{\mathrm{A}}-{\overrightarrow{\mathrm{\upsilon }}}_{\mathrm{B}}$ at $\mathrm{t}=\frac{\mathrm{\pi }}{2\mathrm{\omega }}$ is given by