As \(a = \frac{{dv}}{{dt}} = \frac{{dv}}{{dx}}.\frac{{dx}}{{dt}}\)
\(\therefore a = \frac{1}{2}{(180 - 16x)^{ - 1/2}} \times ( - 16)\;\left( {\frac{{dx}}{{dt}}} \right)\)
\( = - \;8\;{(180 - 16x)^{ - 1/2}} \times \;v\)
\( = - \;8\;{(180 - 16x)^{ - 1/2}} \times \;{(180 - 16x)^{1/2}}\)
\( = - \;8\;m/{s^2}\)