I have a question about this question that I hope someone can answer. QUESTION: "A student on a piano stool rotates freely with an angular speed of 29.5rps. The student holds a 1.25 kg mass in each outstretched arm, .759m from the axis of rotation. The combined moment of Inertia of the student and the stool (ignoring the two masses) is 5.430kg.m^2 (a value that remains constant). a.) As the student's arm are pull inward the angular speed is 3.54 rps. Determine the distance the masses are from the axis of rotation at this time (consider the masses to be modeled a mass-points).<I KNOW THE ENGLISH IS CHOPPED UP, BUT THIS IS HOW IT WAS WRITTEN ON THE PAPER.> b.)Calculate KEfinal\KEINITIAL MY THOUGHT PROCESS: This seems to me that the answers lie in utilizing the work-energy theorem which says that the net work done by external forces in a rotating rigid object about a fixed axis equals the change in the object's rotational energy. ie (.5*IW^2)final-.5*IW^2)initial=Sum of Work Where I=moment of inertia of an extended rigid object and W=instantaneous angular speed To get radius (r) we know that W*r=tangential Velocity we also know that I=m*r^2 MY questions: -I don't understand how you can "ignore the two masses" in the calculation of I to get 5.430kg.m^2. -How do I find the I of the whole system if the 2 masses are ignored -Do I need to find the tangential velocity value of angular speed in order to find the R? -If so, how would I go about doing it? Thanks for reading this. Hopefully somebody can make sense of all this.