From Mechanics

The force on the particle down the plane is

\displaystyle mg\sin {{30}^{\circ }}=m\times 9\textrm{.}81\times \frac{1}{2}=m\times 4\textrm{.}9\ \text{N}

Using Newton´s Second Law \displaystyle F=ma\ gives

\displaystyle \begin{align} & m\times 4\textrm{.}9=ma \\ & \text{ or} \\ & a=4\textrm{.}9\ \text{m}{{\text{s}}^{-2}} \\ \end{align}

Note this result is true independent of the mass of the particle. The fact that all bodies slide down a smooth plane with the same acceleration was an important discovery in the development of modern mechanics.