At time t = 0, a disk of radius 1m starts to roll without slipping on a horizontal plane with an angular acceleration of $\mathrm{\alpha }=\frac{2}{3}$ rad s^–2. A small stone is stuck to the disk. At t = 0, it is at the contact point of the disk. The maximum height (in m) reached by the stone measured from the plane is $\frac{1}{2}+\frac{\mathrm{x}}{10}$ . The value of x is ________. [Take g = 10 ms^–2.]