Answer:- 2g/3r refers to the magnitude alpha of angular acceleration of cylinder when the block descends.
The linear acceleration a of the declining down block as well as the angular acceleration α of the cylinder are connected by the equation a=Rα
• Since the string do not slip over the cylinder. The term R refers to the radius of the cylinder.
• Newton’s second law can be practical to both the cylinder and the block to get the respective equations of motion.