the point of contra flexure is a point where
Contraflexure In a bending beam, a point is known as a point of contraflexure if it is a location at which no bending occurs. It is also known as an inflection point. In a bending moment diagram, it is the point at which the bending moment curve intersects with the zero line. In other words where the bending moment changes its sign from negative to positive or vice versa. Knowing the place of the contraflexure is especially useful when designing reinforced concrete or structural steel beams and also for designing bridges.
Center of mass A body's center of gravity is the point around which the resultant torque due to gravity forces vanishes. Where a gravity field can be considered to be uniform, the mass-center and the center-of-gravity will be the same. However, for satellites in orbit around a planet, in the absence of other torques being applied to a satellite, the slight variation (gradient) in gravitational field between closer-to (stronger) and further-from (weaker) the planet can lead to a torque that will tend to align the satellite such that its long axis is vertical. In such a case, it is important to make the distinction between the center-of-gravity and the mass-center. Any horizontal offset between the two will result in an applied torque.