Two blocks ( P and Q ) with respectively masses 2 kg and 1.5 kg are joined by a massless thread. These blocks are mounted on a frictionless pully…

Two blocks ( $\displaystyle P$ and $\displaystyle Q$ ) with respectively masses $\displaystyle 2$ kg and $\displaystyle 1.5$ kg are joined by a massless thread. These blocks are mounted on a frictionless pully which is fixed on the edge of a cube $\displaystyle (S)$, as shown in the figure below. Block $\displaystyle P$ is positioned on the top surface which has no friction and block $\displaystyle Q$ is in contact with side-surface, having coefficient friction $\displaystyle \mu$. The cube $\displaystyle (S)$ moves towards the right with acceleration of $\displaystyle \frac{g}{2}$, where $\displaystyle g$ is gravitational acceleration. During this movement the block $\displaystyle P$ and $\displaystyle Q$ remain stationary. The value of $\displaystyle \mu$ is $\displaystyle \_\_\_\_$. (take $\displaystyle \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )