A spool rests on the horizontal surface on which it rolls devoid of slipping. The middle part of the spool consists of a radius r and is very light compared by the ends of the cylinder which encompass radius R and altogether encompass mass M. A string is wrapped about the middle part so you can pull horizontally (from the middle part top side) with a force T.
i) Find out the net frictional force on the spool in terms of T, r and R.
ii) Determine the condition for the linear acceleration of the spool to surpass T/M?
iii) Which direction does the friction force point if the acceleration is less than T/M? In which direction the friction force points if the acceleration is more than T/M?