Rolling Under The Influence

free-body diagram

The free-body diagram looks like the one above( sorry for the poor clarity of the same). From there we can write equations of motion as:

$\mathbf{translation}$ :

$ma=\,qE-f\;\;\;---(i)$

$\mathbf{rotation\,about\,center\,of\,mass:}$

$fr=\,I\alpha$

$\rightarrow\,fr=\,\displaystyle\frac{2mr^2\alpha}{5}$

$\rightarrow\,fr=\,\displaystyle\frac{2mr^2a}{5r}$ $($ Since for pure rotation/no slipping $a=\alpha\,r)$

$\rightarrow\,f=\displaystyle\frac{2ma}{5}\;\;\;----(ii)$

From $(ii)$ and $(i)$ we have,

$\displaystyle\frac{7ma}{5}=qE$

$\rightarrow\,a=\displaystyle\frac{5qE}{7m}$

Plugging in the values in S.I. we have $\displaystyle\,a=\boxed{\frac{5}{7}}$ .