The potential energy of a particle in a certain field has the form U = a/r2 - b/r, where a and b are positive constants, r is the distance from the centre of the field. Find:
(a) The value of ro corresponding to the equilibrium position of the particle; examine whether this position is steady;
(b) The maximum magnitude of the attraction force; draw the plots U (r) and Fr (r) (the projections of the force on the radius vector r).