If an object if forced to vibrate at its natural frequency it will vibrate at its maximum amplitude.
We call this effect Resonance.
The larger the mass of an object, the lower its natural frequency.
We did an experiement in class with test tubes partially filled with water so that each contained a column of air. The one with the shortest column of air (most water) had the least mass of air and therefore the highest frequency, the empty tube, with the greatest mass of vibrating air had the lowest frequency. Similarly on a guitar the thickest string (the one with the most mass) has a low freqency (deep note) while the thinest string has the highest note.
You may have seen film of a singer finding a glasses natural frequency and causing the glass to shatter. In class we looked at a movie of the wind causing the old Tacoma Narrows Bridge to resonate at it's natural frequency.
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