If a structure is excited at its inherent natural frequency by daily forcing, what is the likely consequence?

• A. Resonance leading to large amplitude oscillations.
• B. Loss of mass.
• C. Immediate structural failure.
• D. No observable effect.

Answer: (A)

Resonance is the key idea here: when a structure is driven at its natural frequency, the energy input from each cycle adds up in phase with the motion. That keeps pumping energy into the same vibrating mode, so the amplitude grows. If the daily forcing continues and damping is not enough to dissipate the energy, the vibrations can become very large. This is why resonance often leads to large amplitude oscillations.

Loss of mass isn’t caused by this kind of vibrational interaction, and immediate structural failure isn’t guaranteed—extreme but not automatic. No observable effect isn’t right either, since you would expect to see noticeable vibrations when resonance occurs.