Conservation of Energy and Momentum: For the structural engineer, it is important to keep in mind the principles of conservation of energy and momentum. This often helps predict the behavior of a building under wind and earthquake loads. Pendulum systems: in this context, evaluating the characteristics of a structural pendulum is a very important structural concept. This helps in devising stabilizing systems that bring the structure back into equilibrium. while giving it sufficient elasticity to accept and bear external loads. For example, skyscrapers or bridges can start swaying back and forth after being hit by a strong wind. Free Vibration: Free vibration occurs when a building is out of its stable equilibrium. This may be due to an earthquake or similar natural event. As a result, the building vibrates or swings without any additional external interference. Expressed in cycles of vibration, with the number of cycles representing the natural frequency of the building, free vibration is important. It is possible to reduce and completely stop free vibration by using damping elements.