The Importance of Static Balance: Staying Safe and Strong

The concept of static equilibrium, more precisely static mechanical equilibrium, is used in physics to describe a stationary state in which the relative position of the components of a system does not change with time. It doesn’t mean they don’t move, they can, what doesn’t change is the relative position between the components.

In other words, in the state of static equilibrium the system is at rest or its center of mass moves at a constant velocity. This concept is implicit in the Law of Inertia, the first of Newton’s three laws: Every body perseveres in its state of rest or uniform and rectilinear motion unless it is forced to change its state by forces impressed on it.

The most common definition of static equilibrium uses net force: an object is in static equilibrium when the sum of the forces acting on it (net or resultant force) equals zero. Both translational forces and torsion forces are taken into account, therefore an object is in static equilibrium if it is in translational equilibrium and in rotational equilibrium.

Another broader definition defines the state of static equilibrium as that state of an object whose position in space has a potential energy gradient equal to zero. In this definition, the object can move at a constant speed and implies that, although it may not appear so in our observation frame, it is always possible to find a frame of reference with respect to which the object is stationary. I challenge you to do the following practice!