Static and Dynamic Equilibrium

The state equilibrium can be observed in physical and chemical systems. Equilibrium can be static or dynamic in nature.

A book lying on the table is an example of static equilibrium. The forces of action and reaction cancel each other and no change takes place. Thus, it is a case of static equilibrium.

On the other hand, when an escalator is coming down and a passenger is going up at the same speed, it is a case of dynamic equilibrium. Here, because both are moving in opposite directions and at the same speed, no net change takes place.