1. The problem statement, all variables and given/known data Over the years, buildings have been able to be built out of lighter and lighter materials. how has this affected the natural oscillation frequencies of buildings and the problems of resonance due to passing trucks, airplanes, or by wind and other natural sources of vibration? 2. Relevant equations None 3. The attempt at a solution I don't think I fully understand the question. Upon reading I have found natural frequency equations and the concept of resonance as it applies to damping but I don't see how the mass of the materials effect these. My initial thought was that the natural frequencies were higher, making it less likely for passing frequencies to get close to the natural frequencies.