\item $v_{average}=\frac{1}{t_0}\int_{0}^{t_0} v(t) dt
=-\frac{eE}{m}\frac{1}{t_0}[\frac{t^2}{2}]_{0}^{t_0}
=-\frac{eE}{m}\frac{t_0}{2}=:-\frac{eE}{m}\tau$,
\item $v_{average}=\frac{1}{t_0}\int_{0}^{t_0} v(t) dt
=-\frac{eE}{m}\frac{1}{t_0}[\frac{t^2}{2}]_{0}^{t_0}
=-\frac{eE}{m}\frac{t_0}{2}=:-\frac{eE}{m}\tau$,