Internal forces are generated within a body due to the interaction between its particles. These forces include tension, compression, and shear. The internal forces exist in collinear pairs of equal magnitude but opposite directions. They cancel out between all the connected parts, resulting in the body's equilibrium. The weight of a body is an external force represented by a single resultant force acting through the body's center of gravity. It is the point where a body balances itself, provided no external force acts on it. A symmetrical or uniform body has its center of gravity at its geometric center. However, for an irregular or non-uniform body, it is off-centered towards the heavier side. Consider a beam attached to a crane at the center, with loads connected at its ends. If load on one side becomes heavy, the center of gravity will shift away from the centerline of the beam, potentially causing tipping. The center of gravity must be identified to ensure stability, and the lifting hook should be placed directly above it.