In this inquiry lab from Hoop There It Is, students use rubber bands to attach washers to a meter stick in order to develop a working definition for rotational inertia. The four trials of the lab have students vary the number of washers and the distance of the washers from the pivot point in order to see what factors affect how hard it is to rotate a rigid object.
This is a quick, easy-to-set-up lab that can be completed independently or in pairs. The lab concludes by requiring students to synthesize all parts of the lab in order to write an overall general rule about rotational inertia, before ever learning the formal definition.
Follow up this lab with reading from a textbook, lecture notes, or applications of rotational inertia and angular momentum.