> Suppose there is human statue of cement in standing position. We human
> being can remain in standing position. But why can't this statue remain
> standing even if it is exact like our body?
There are two types of equilibrium: stable and unstable. Both are
slope=0 points in a potential energy curve, but one curves up and the
other curves down. A standing human is better modeled with unstable
equilibrium. With periodic small corrections, an unstable equilibrium
can be maintained, but a statue cannot make those corrections.