Mechanical equilibrium

In classical mechanics, a particle is in mechanical equilibrium if the net force on that particle is zero.:39 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.:45–46An important property of systems at mechanical equilibrium is their stability.A stationary object (or set of objects) is in 'static equilibrium,' which is a special case of mechanical equilibrium. A paperweight on a desk is an example of static equilibrium. Other examples include a rock balance sculpture, or a stack of blocks in the game of Jenga, so long as the sculpture or stack of blocks is not in the state of collapsing.