Other contributors have said "What ia an equilibrium system?" is the same question as "When is a system in a state of equilibrium?" If you believe that these are not asking the same thing and should be answered differently, click here
Yes equilibrium is the state when there is no evolution in a population. In life there is no such thing as equilibrium because all populations evolve.Hope that helps! :)
State of equilibrium means that there is a balance of forces summing to zero, or no acceleration. If there are no forces, there will be no acceleration or change of velocity.
Velocity can be...