From Mechanics

Using \displaystyle {{v}^{\ 2}}={{u}^{\ 2}}+2as\ \ gives

\displaystyle \begin{align} & {{24}^{2}}-{{9}^{2}}=2\times a\times 495 \\ & 576-81=990 \times a \\ & a=\frac{495}{990}=0\textrm{.}5\ \text{m}{{\text{s}}^{-2}} \\ \end{align}