(a) Effective Date of Original Rules. These rules will take effect on January 1, 1981. They govern all proceedings brought after they take effect and also all proceedings then pending, except to the extent that in the opinion of the court their application in a particular proceeding pending when the rules take effect would not be feasible or would work injustice, in which event the former procedure applies. (b) Effective Date of Amendments. Amendments to these rules will take effect on the day specified in the order adopting them. They govern all proceedings brought after they take effect and also all proceedings then pending, except to the extent that in the opinion of the court their application in a particular proceeding pending when they take effect would not be feasible or would work injustice, in which event the former procedure applies.