Effect of resonance

This demonstration shows that a cantilever experiences significant vibration at resonance.

   
a) A medical shaker and two cantilevers                       b) Simulated shaking table test
Fig. 16-10: Demonstration of resonance

Fig. 16-10a shows a medical shaker that can generate vibrations at a frequency of 5 Hz or 10 Hz in three perpendicular directions. A steel ruler and a longer and thicker steel ruler are mounted on a wooden plate that can be firmly placed on the shaker as shown in Fig. 16-10b. Both rulers are selected to have their fundamental natural frequencies slightly less than 5 Hz.

Switch on the shaker at the frequency of 10 Hz and it will be seen that the two rulers vibrate with very small amplitudes in comparison with the movement of the shaker.

Change the vibration frequency from 10 Hz to 5 Hz and it will then be observed that both rulers vibrate with significant amplitudes as the fundamental frequencies of the rulers are close to the shaking frequency.