5-4


 * May 5th, 2009

Agenda: Homework Check Daily Question More on Harmonics and Standing Waves Resonance Homework Check:** Today we began class by having Mr. Manning check the homework assignment from Friday, page 23 numbers 1-3.

A standing wave is produced in a tube 2 meters long. The tube has one open end and one closed (fixed) end. 1.) Draw the standing wave in the 2 meter long tube if the 5th harmonic is sounded. 2.) How long is the wavelength in the tube? Because we have 5 sections (one quarter each), we have to divide 2 meters by 5. The number we get is .4, which represents the length of one quarter of a wave. Then we multiplied .4 by 5 to get a total length of 1.6 meters.
 * Daily Question:**

3.) To make sure everyone was getting an understanding of harmonics and fundamentals, Mr. Manning then asked us to draw the same scenario with 2 fixed ends. Start the wave with an antinode. We learned that the fundamental of 2 open ends was one half, unlike in the first problem when each was one quarter. We then totaled the number of wavelengths for a total of 2.5 wavelengths. Like before we divided 2 by 5 which was .4 and then multiplied by 2 to find the length of one wavelength, .8 meters.

Mr. Manning connected a motor to a string to prove that by changing the length of a string, we are able to change the harmonic. We also learned that by changing the tension of the string you can also change the harmonic.
 * More work on Harmonics:**

A second demo Mr. Manning did was spinning a tube to let air over the lip. Depending on how fast or slow he twirled the tube we were able to hear the fundamental harmonic, the second, third, fourth and fifth but we were not able to make it fast enough to hear the sixth. This demonstration was really cool! Below is a picture of Mr. Manning vigorously spinning the tube.

The third demo Mr. Manning did was by using a test tube in a tube of water with a tuning fork. When he but the vibrating tuning fork over the tube of water, we were able to hear a tone, which is where the node was.

Another demo Mr. Manning did was pushing a bowling ball to demonstrate that you have to match the frequency to increase the amplitude. This demonstration was demonstrating resonance. Below is a picture of Mr. Manning matching the frequency of the bowling ball. Another example Mr. manning did to prove this theory was with a music box player. When the player was held in the air it was very quite, but when he put it on the table the table resonated the music player.

Before ending a really fun day of demonstrations, Mr. Manning reminded the class to make sure everyone is keeping up with there work and preparing for the test. Have a great day!!

Test and Reading guide due on Thursday Rollercoaster Final Project due Friday **
 * Homework: