1. The problem statement, all variables and given/known data Two disks are spinning freely about axes that run through their respective centres (see figure below). The larger disk (R1 = 1.42 m) has a moment of inertia of 1070 kg · m2 and an angular speed of 4.2 rad/s. The smaller disk (R2 = 0.60 m) has a moment of inertia of 909 kg · m2 and an angular speed of 8.0 rad/s. The smaller disk is rotating in a direction that is opposite to the larger disk. The edges of the two disks are brought into contact with each other while keeping their axes parallel. They initially slip against each other until the friction between the two disks eventually stops the slipping. How much energy is lost to friction? (Assume that the disks continue to spin after the disks stop slipping.) 2. Relevant equations Conservation of angular momentum. 3. The attempt at a solution I attempted the problem by first using the cons. of angular momentum to find the final angular speed of the 2 disks, then subtracted the initial kinetic energy by the final kinetic energy of the system to obtain energy lost, though I apparently arrived at the wrong answer. What is the correct approach to this problem?