A solid sphere of radius R carries a charge Q + q distributed uniformly over its volume. A very small point like piece of it of mass m gets detached…

A solid sphere of radius $\displaystyle R$ carries a charge $\displaystyle \mathrm{Q}+\mathrm{q}$ distributed uniformly over its volume. A very small point like piece of it of mass m gets detached from the bottom of the sphere and falls down vertically under gravity. This piece carries charge q. If it acquires a speed $\displaystyle v$ when it has fallen through a vertical height $\displaystyle y$ (see figure), then : (assume the remaining portion to be spherical).