Translational Equilibrium

A system that is in Translational equilibrium is a system that has no change in its linear motion (straight line motion).  Simply put the velocity will not change for a system that is in translational equilibrium.  It is important to point out that the velocity "will not change", this doesn't mean the object is not moving, it just means if its not moving, it wont move, if it is moving the rate of motion will not change. If the velocity doesn't change then the acceleration is equal to 0.  This means that the sum of all of the forces, when "added" together is equal to 0.  Becareful this doesn't mean that all of the forces are zero, instead they simply cancel each other. Rotational Equilibrium

A system that is in rotational equilibrium is a system that has no change in its rotational motion.  Simply put the rotational velocity will not change for a system that is in rotational equilibrium.  It is important to point out that the rotational velocity "will not change", this doesn't mean the object is not spinning, it just means if its not spin, it wont spin, if it is spinning the rate of the spin will not change. If the rate of the spin doesn't change then the rotation acceleration is equal to 0.  This means that the sum of all of the torques, when "added" together is equal to 0.  Becareful this doesn't mean that all of the torques are zero, instead they simply cancel each other. Equilibrium

equilibrium refers to system were both the sum of the torques and forces are equal to zero, meaning it motion is constant.

Sum of the Forces Sum of the Torques Problem set