Consider a fixed uniformly charged insulating sphere with radius R and total charge +Q. A point charge -q (q Q) with mass m is released from rest at…

Consider a fixed uniformly charged insulating sphere with radius $\displaystyle R$ and total charge +Q. A point charge -q $\displaystyle (\mathrm{q} \ll \mathrm{Q})$ with mass m is released from rest at a distance of 3R from the centre of the charged sphere. When the point charge reaches the surface of the sphere, its speed is : ( $\displaystyle \epsilon_0$ is the permittivity of vacuum, neglect gravitational forces).