Hello, I'm having some difficulties keeping when Linear/Angular Momentum and Kinetic Energy are conserved straight. So far I believe that Kinetic energy is conserved when no outside/non-conservative forces are acting on an object. It is conserved only in perfectly elastic collisions, which only occur at the atomic level(?) Then it decreases in inelastic collisions and increases in explosions. Linear momentum is conserved when Kinetic Energy is conserved, ie, no outside forces acting on the object and in all types of collisions. Angular momentum is conserved when the net torque acting on an object is 0. Here's my big question on this one, how do I know when the net torque is 0? I believe that torque is the tendency of an object to rotate, so when there's no rotation is there no torque? I just need a little bit of clarification on all of these. Thank you so much for your help!