A spool with thread wound on it, of mass m, rests on a rough horizontal surface. Its moment of inertia relative to its own axis is equal to I = ymR2, where y, is a numerical factor, and R is the outside radius of the spool. The radius of the wound thread layer is equal to r. The spool is pulled without sliding by the thread with a constant force F directed at an angle a to the horizontal (Fig. 1.63). Find:
(a) The projection of the acceleration vector of the spool axis on the x-axis;
(b) The work performed by the force F during the first t seconds after the beginning of motion.

R