this is an euler's disk.momentum, potential energy, and kinetic energy. aw, look at you watching sports. we're betting to see if koothrappali can hold his breath longer than the disk can spin. its weight and smoothness, along with the slight concavity of the mirror, means it can spin for a long time. but raj is from india, which means he's no slouch at holding his breath. okay, i want in. ten bucks says i'll lose interest before that thing stops spinning. hey, sheldon, i found a great restaurant for date night. kind of busy right now. oh, an euler's disk! fun! yeah, we're seeing if raj can hold his breath longer than it. oh. immature. how ya doing? mm. he's not gonna make it. yes, he is! you know, deep-sea divers holding their breath for several minutes