A hollow steel shaft of outer diameter 2 in., inner diameter 1.5 in., and length 30 in. carries a solid disc of diameter 15 in. and weight 100 lb. Another hollow steel shaft of length 20 in., carrying a solid disc of diameter 6 in. and weight 20 lb, is attached to the first disc, as shown in Fig. 9.51. Find the inner and outer diameters of the shaft such that the attached shaft-disc system acts as an absorber.
