What are the 3 types of equilibrium?
mechanical, thermal and material equilibrium
In classical mechanics, a particle is in mechanical equilibrium if the net force on that particle is zero. By extension, a physical system made up of many parts is in mechanical equilibrium if the net force on each of its individual parts is zero.
Two physical systems are in thermal equilibrium if no heat flows between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of thermodynamics.
Material (chemical) equilibrium is achieved when no net chemical reactions is occurring and composition is constant.