Tall buildings are designed to sway in the wind. In a 100-km/h wind, for example, the top of the 110-story

Tall buildings are designed to sway in the wind. In a 100-km/h wind, for example, the top of the 110-story Sears Tower oscillates horizontally with an amplitude of 15 cm. The building oscillates at its natural frequency, which has a period of 7.0 s.