A block pressed against the vertical wall is in equilibrium.if μ = 0.3, the acceleration of the block will be:

If μ = 0.3Maximum value of resisting force will beFlim = μN = 0.3 mgBut have driving force is mg/2.Therefore the friction will be kinetic nature; the block will slid down. Hence acceleration of the blocka = mg2-0.3 mgm = 0.2 g = g5↓