Question

the relationship between double differentiation and movement of object

Answer 1

The moments of an object measure its tendency to rotate around an axis. The center of mass of an object with even density is the point where the object would be perfectly balanced if it were suspended from that point. The center of mass is based on the object's moments. For a two-dimensional system, the object is a region defined by two functions, and has two moments: Mx and My. For two functions f(x) and g(x), where  over the interval [a,b].
Double defferentiation= The second derivative can be used as an easier way of determining the nature of stationary points (whether they are maximum points, minimum points or points of inflection). A stationary point on a curve occurs when dy/dx = 0.

Answer 2

double differentiation =0= equilibrium
double differentiation >0=object comes back to original position
double differentiation <0=object moves away