Center of gravity:

The center of gravity is geometric property of any object. The center of gravity is average location of the weight of an object. We can describe the motion of any object through space in the terms of the translation of the center of gravity of the object from 1 place to other and the rotation of the object about the center of gravity if it is free to rotate. If the object is restricted to rotate about some other point, like a hinge, we can still describe the motion of it. In flight, rockets and airplanes both rotate about their centers of gravity. The centre of mass/gravity is not necessarily inside the object. So as to balance the object against gravity with the single force, that force should lie in a vertical line which runs through the centre of gravity.

 For objects having symmetry, the center of gravity is located along the axis of symmetry always. The center of gravity of the extended body or system of masses is distinguished by the fact that it will remain at rest or moving at the constant velocity unless body is acted on by a external force .The kite rotates about the bridle point. But the trim of the kite still depends on location of the center of gravity relative to the bridle point, as for every object the weight always acts as the center of gravity.

By determining the center of gravity (cg) is a complicated procedure as the mass may not be uniformly distributed throughout the object. For the general shaped object, there is a simple mechanical way to determine center of the gravity: If we balance the object using a string or an edge, the point at which the object is balanced is center of the gravity. In Step 1, you hang the object from any point and you drop the weighted string from the same point. Draw a line on the object along with the string. For Step 2, repeat the procedure from other point on the object you now have 2 lines drawn on the object which intersect. The center of gravity is point where the lines intersect. This procedure works well for the irregularly shaped objects which are hard to balance.