1. The problem statement, all variables and given/known data In a demonstration, a bicycle wheel with moment of inertia = .37 kg*m^2 is spun up to 14 rad/s, rotating about a vertical axis. A student hold the wheel while sitting on a rotatable stool. The student and the stool are initially stationary and have a moment of inertia equal to 3.6 kg*m^2. If the student turns the bicycle wheel over so its axis point in the opposite direction, with what angular velocity will the student and stool rotate? Assume the wheel, student, and stool all have the same axis of rotation. 2. Relevant equations Im not entirely sure if you need the equation for angular momentum, or just to know that it is conserved. Ill give the equation anyways. Angular Momentum Equation: L=I*ω Moment of Inertia Equation: I = m*r^2 3. The attempt at a solution I figured that this question is all about the conservation of angular momentum. If I add the moment of inertia of the stool and student to the negative of the inertia for the bicycle wheel (because its now upside-down, right? ) I would get the total moment of inertia for the system. I have no idea how to proceed from here, becase the equation for moment of inertia is I = m*r^2, and I dont have an r to use. Maybe I need to look into the angular momentum equation some more (derivative of that equation to find the change of ω perhaps?) I feel like this should be an easy problem (this is a reading review problem supposedly) but its just not clicking for me. Any help is greatly appreciated.