A solid sphere of mass 1 kg and radius 1 m rolls without slipping on a fixed inclined plane with an angle of inclination  $\theta ={30}^0$ from the horizontal. Two forces of magnitude 1N each, parallel to the incline, act on the sphere, both at distance  $r=0.5$m from the centre of the sphere, as shown in the figure. The acceleration of the sphere down the plane is______$m{s}^{-2}$. (Take  $g=10m{s}^{-2}$)