A spool (consider it as a double disc system joined by a short tube at their centre) is placed on a horizontal surface as shown Fig. A light string wound several times over the short connecting tube leaves it tangentially and passes over a light pulley. A weight of mass `m` is attached to the end of the string. The radius of the connecting tube is r and mass of the spool is `M` and radius is `R`. Find the acceleration of the falling mass `m`. Neglect the mass of the connecting tube and slipping of the spool.

Answer

`"["(2mg)/(2m+3m((R)/(R-r))^(2))"]"`