a plank having mass 6.6 kg rides on top of two identical solid cylindrical rollers each having radius 4.6 cm and mass 1.9 kg. the plank is pulled by a constant horizontal force 6 n applied to its end and perpendicular to the axes of the cylinders (which are parallel). the cylinders roll without slipping on a flat surface. there is also no slipping between cylinders and plank. m r m r f m find the acceleration of the plank. answer in units of m/s 2 .