Where an existing public limited company proposes to take up a new business, which is covered in the "other objects" of the Memorandum in the case of a company formed on or after 15-10-1965 or covered in the object clause of a company formed before 15-10-1965, the said business can be undertaken by the company only after the proposal is approved by the members by a special resolution.
However, section 149 does not apply to a private company.
You are free to change your objects by Board resolution.