A 3D-Printed Wheel with Constant Mass and Variable Moment of Inertia for Lab and Demonstration

• Eric Hazlett ^[1] ; Andrés Aragoneses ^[2]
  1. [1] Carleton College

     Carleton College

     City of Northfield, Estados Unidos

     
  2. [2] Eastern Washington University

     Eastern Washington University

     Estados Unidos

     
• Localización: The Physics Teacher, ISSN 0031-921X, Vol. 56, Nº. 8, 2018, págs. 535-537
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • We present a versatile experimental apparatus for exploring rotational motion through the interplay between the moment of inertia, torque, and rotational kinetic energy of a wheel. The heart of this experiment uses a 3D-printed wheel along with easily accessible stock components that allow for the adjustment of the moment of inertia while keeping the total mass of the wheel constant. The wheel can act as a massive pulley of variable moment of inertia that allows students to measure the moment of inertia of the bare wheel by applying a constant torque to the system. The wheel can also be used to explore rotational kinetic energy in the form of races down ramps. The 3D-printed aspect of this wheel allows anyone with access to a 3D printer to create, explore, and modify this wheel at a low cost, allowing for more flexibility and accessibility for student and instructor exploration and modification. In the study of linear kinematics, it is easy to investigate how systems evolve with variable mass. With rotational motion the situation is more complicated due to the fact that the moment of inertia depends not only on the mass, but also on the distribution of the mass. This can be demonstrated in the form of massive pulleys in Atwood machines and in a rolling race of objects of varying mass and moment of inertia. For lab explorations it is best to isolate a single variable that can be changed. For rotational motion it is difficult to find a wheel with constant mass but different moments of inertia. There do exist examples that solve this problem, but they require workshop access and cannot act as pulleys. To address this issue we have designed a wheel whose moment of inertia can easily be created and manipulated while the mass of the system remains constant, providing an accessible, flexible, and robust apparatus to explore the interplay between moment of inertia and torque and rotational kinetic energy.