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**fardeen_gen** A ring of radius $\displaystyle r$ having the charge $\displaystyle Q$ distributed uniformly over its surface is fixed in $\displaystyle Y-Z$ plane with centre at origin. A particle of mass $\displaystyle m$ and charge $\displaystyle (-q)$ is placed at a point $\displaystyle P$ which is at a distance $\displaystyle d$ from the centre of the ring. Particle is attached to one end of a spring of spring constant $\displaystyle k$. The other end of spring is fixed at origin. Find the minimum velocity to be imparted to $\displaystyle P$ (Consider motion in $\displaystyle X-Y$ Plane) so that the spring is not compressed.