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 from the bottom of the sphere and falls down vertically under gravity. This piece carries charge $$q$$. If it acquires a speed $$v$$ when it has fallen through a vertical height $$y$$ (see figure), then (assume the remaining portion to be spherical)