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 I figure ) then : ( assume the remaining portion to be spherical ) 

• A

  $v^2=y\left[\frac{qQ}{4\pi {\in }_{0}R\left(R+y\right)m}+g\right]$

• B

  $v^2=y\left[\frac{qQ}{4\pi {\in }_0{R}^{2}ym}+g\right]$

• C

  $v^2=2y\left[\frac{qQ}{4\pi {\in }_{0}R\left(R+y\right)m}+g\right]$

• D

  $v^2=2y\left[\frac{QqR}{4\pi {\in }_0{\left(R+y\right)}^{3}m}+g\right]$