Birds Bats and LEGO Limbs Modeling the Variable

Birds, Bats, and LEGO Limbs: Modeling the Variable Moment of Inertia During Locomotion in a Lab for IPLS Students Melissa Vigil, Department of Physics, Marquette University Introduction Student Activity Prompts: Analyzing gross motor motion is important to physical therapy students in IPLS courses. Using the work of Thollesson & Norberg (J. Exp. Bio, 1991) as a starting point, students use LEGO bricks to model the changes in moment of inertia of 2 limbs both from the sum of mr terms and from the movement of the model as physical pendulum. 1. Build a slab-like LEGO limb for which y = 2 -pips thick and which is symmetrical around the z-axis. 2. Use at least one physical method and one mathematical method to determine x. CM for the LEGO limb. 3. Determine values for the moment of inertia using the two mathematical models shown. Describe what methods you use to limit your measurement uncertainty. Lab Development Goals: 1. Use biologically relevant examples in the lab. 2. Use materials that students could use at home or in the lab 3. Focus on mathematical models. 4. Have at least two methods to arrive at the target value. 5. Build in opportunities metacognitive discussion and self-assessment. Pivotal Pedagogy: 4. How could you change the oscillation period of your LEGO limb? Using all the same set of bricks, create another physical pendulum with a notably different oscillation period. Test your predictions. 1. Encourage student discussions about the assumptions and simplifications used in mathematical modeling of physical systems. 2. Encourage student discussion of design choices and problem-solving strategies, especially in cases where there are multiple ways to reach the same answer. 3. Encourage use of spreadsheets for longer & repeated calculations. 4. Encourage student creativity and ownership rather than reliance on Google & Chegg. 5. Discuss the functional morphology or gait of a person or animal species as it relates to your data and observations. References: Student Testing & Image Credits: Thollesson, M. & U. M. Norberg. Moments of Inertia of Bat Wings and Body. J. exp. Biol. 158, 19 -35. 1991 Mike Nichols, Annie Carani, Kate Piper, Yana Rawinski, Eugenie Acra, Manar Al-Rubaye, & Saad Khawari, Marquette University Van Den Berg, C. & J. M. V. Rayner. The Moment of Inertia of Bird Wings and the Inertial Power Requirement for Flapping Flight. J. exp. Bio 198, 1655 -1664. 1995. Deanna Moses, Delavan HS, Delavan, WI