5-4-09

On May 5th in Mr. Mannings's Physics class there was:

1. A homework check (Standing Waves Harmonics and Resonance...p.20-23) 2. A daily question: Draw the 5th harmonic in a two meter tube with one fixed and one open end. Find the length of one full wavelength. (Ans: 1.6 meters) 3. A review on harmonics and standing waves. Two antinodes in a standing wave create constructive interference, which increases the amplitude of a wave. Two nodes in a standing wave create destructive interference. Two waves can create a standing wave if they are traveling in opposite directions in the same medium and have the same frequency. 4. An introduction to resonance: the fundamental natural frequency at which an object vibrates is called its resonance frequency. It is important to note that also vibrate at the harmonics of the resonant frequency. When an object vibrates at its resonant frequency, a standing wave pattern is created. If an object vibrates at a specific frequency, it is possible to cause another object to resonate.

Mr. Manning demonstrated resonance using two hollow wooden blocks with tuning forks attached to them. He struck one of the attached tuning forks to create a resonating frequency; the other hollow wooden block, adjacent to the first one, received the frequency as it made its own sound. This happened because the first block caused the air molecules inside to vibrate and then transfer into the other block. Some examples of resonating objects are whirling tubes, coins, and springs.