A system consists of three masses \(\mathrm{m}_1\) \(\mathrm{m}_2\) and \(\mathrm{m}_3\) connected by a string passing over a pulley P. The mass \(\mathrm{m}_1\) hangs freely and \(\mathrm{m}_2\) and \(\mathrm{m}_3\) are on a rough horizontal table (the coefficient of friction \(\mu\) ). The pulley is frictionless and of negligible mass. The downward acceleration of mass \(\mathrm{m}_1\) is: (Assume \(\mathrm{m}_1 = \mathrm{m}_2 = \mathrm{m}_3 = \mathrm{m}\))