Mechanical Waves

You are down at the ocean looking at all of those waves coming to shore and then going back. What is a wave, though? It is a disturbance that transfers energy from place to place. The main type of wave I have been learning about is the MECHANICAL WAVE. A mechanical wave is a type of wave that requires a medium to travel through. Now, you may want to know what a medium is. A medium is material, such as a gas, a liquid, or a solid, through which a wave travels. There are two types of mechanical waves. Those waves are TRANSVERSE and LONGITUDINAL WAVES. What is the difference between those waves? A transverse wave is a wave that moves the medium at right angles to the direction in which the waves travel. A transverse wave has three main parts: the crest which is the high point of the wave, the trough which is the low part of the wave, and the rest point which is the middle of the wave. A longitudinal wave is a wave the moves the medium parallel to the direction in which the waves travel. Similar to a transverse wave, a longitudinal wave also has three main parts: the compressions which are the parts where the coils are close together, the rarefactions which are the parts where the coils are spread out, and the rest point which is the middle of the wave. To visualize a transverse wave, get a partner and hold each end of a jump rope. Then, move the jump rope up and down at different times, so when your partner moves the jump rope up you move it down and vice versa. To visualize a longitudinal wave, get a partner and hold each end of a slinky. Then, one of you should pull the slinky back and let go (don’t take your hands off, just let it go back and forth). The movement of the slinky will be back-and-forth. Then, have your partner do the same.

I believe learning about waves is fun. I mean, you get to use slinkies and ropes to do experiments. In addition, you get to use sand. The unit with mechanical waves was also fun because you got to interact with other people in your class. You may not think about how energy travels, but really everything you do involves waves and energy. When you speak, the person listening is using sound waves to hear you. When you move, you are using chemical energy. Really, waves and energy are really important to our life, just like cells are important to our lives.

These are some more interesting facts:
1. A sound wave is a type of longitudinal wave. When the sound wave comes out of the speaker’s mouth and reaches the listener’s ear, the sound vibrates back and forth in the same direction.
source: The Physics Classroom
hyperlink: http://www.glenbrook.k12.il.us/gbssci/Phys/Class/waves/u10l1c.html

2. To see a transverse wave in motion, go to this website:
http://surendranath.tripod.com/Applets/Waves/Twave01/Twave01Applet.html
source: General Physics Java Applets

3. To see a longitudinal wave in motion, go to this website: http://www.mta.ca/faculty/science/physics/suren/Lwave/Lwave02.html
source: General Physics Java Applets

PICTURES from: (click on pictures to see larger images)
longitudinal: http://library.thinkquest.org/15433/unit5/long1.gif
transverse: http://library.thinkquest.org/15433/unit5/transv1.gif