Comparing Sliding versus Rolling to Determine Moments of Inertia of 3D Printed Cylinders

We present a laboratory activity aimed at having students combine several physics concepts to determine the moment of inertia of a custom 3D printed cylinder. Although the lab could be done without it, 3D printing was used to produce specific custom cylinders having the same outward appearance, size, shape, mass but different interior mass distributions. This serves to highlight for the students that mass distribution is the key factor when considering how an object will rotate. By racing a sliding block against one of the rolling cylinders down inclined ramp, the angle at which the objects tie can be used to determine information about the mass distribution if the friction coefficient is known. The exercise of deriving the angle at which the objects tie brings in concepts additional concepts other than rotation such as forces and torques or conservation of energy. The experimental method also leaves room for students to consider various assumptions in the model leading to a useful discussion of systematic error. We believe that these ideas, along with opportunity for discussion of error and measurements, will make for a

compelling lab activity that could easily be incorporated into introductory classrooms with little or no need for purchase of additional equipment.