Dimension of $\alpha t = \left\lbrack M^{0}L^{0}T^{0} \right\rbrack\therefore\lbrack\alpha\rbrack = \lbrack T^{- 1}\rbrack$ Again $\left\lbrack \frac{v_{0}}{\alpha} \right\rbrack = \lbrack L\rbrack$ so $\left\lbrack v_{0} \right\rbrack = \lbrack LT^{- 1}\rbrack$