Let $m\ \propto E^{x}v^{y}F^{z}$ By substituting the following dimensions: $E = \left\lbrack ML^{2}T^{- 2} \right\rbrack,\lbrack v\rbrack = \left\lbrack LT^{- 1} \right\rbrack,\lbrack F\rbrack = \lbrack MLT^{- 2}\rbrack$ and by equating the both sides $x = 1,y = - 2,z = 0.$ So $\lbrack m\rbrack = \left\lbrack Ev^{- 2} \right\rbrack$