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I'm doing a report on Ocean waves and we have to interview someone so I thought I could send out these question and see who responded. 1. How do ocean waves fit into physics? (Do they have friction, etc.)2. If you were to draw an ocean wave what would you label?3. how do the waves change with each season?4. If you were to do a presentation to a high school class about this topic what would you do?Thanks!
Question Date: 2000-04-11
Answer 1:

1. Ocean waves are a form of energy that can be described with physics. They have a velocity and they do have friction from the air above them and the water around them. When the waves enter shallow water, they spill over in part due to friction from the ocean bottom. There are other waves in physics like sound waves and electrical waves.

2. I would label the crest (top), the trough (bottom), and the distance between the two (amplitude). I would also label the distance between two tops of the wave.

3. Waves are created by the wind from storms. We have storms in the winter because the northern half of the earth is tilted away from the sun during that part of the year. In the summer, the southern half of the earth is tilted away from the earth and there are storms down there. Often times, the waves from the southern half travel all the way up here. So the main difference with each season is where the waves come from. Because we are so far away from the southern half of the earth, the waves from there experience a lot of friction and are smaller.

4. I think a poster with labels would be good. Maybe you could blow air on a container of water and make your own waves. Or use a piece of string to make a wave.

Answer 2:

1.The concept of "waves" appear in many different branches of physics. Ocean waves are an example of "mechanical" waves, or waves that propagate (travel) in an elastic (deformable) media. In this case, the media is the water.

There are two types of mechanical waves:

Transverse waves are waves where the motion of the medium conveying the waves is perpendicular to the direction the wave is traveling. Imagine tying one of a rope to a fixed object and then stretching the rope out. If you then start "snapping" the rope, you can make a wave on the rope. What you see, is that the wave propages down the rope, while the parts of the rope are just moving up and down, or perpendicular to the rope.

Longitudinal waves are waves where the motion of the medium conveying the waves is parallel (back and forth) to the direction the wave is traveling. If instead of a rope, one extended out a giant spring (or slinky!) that was fixed on one end, we can see a different behavior. If we now start pushing and pulling the spring in the same direction it is extended, you can see a "pulse" type wave moving down the spring, and that is a longitudinal wave.

Ocean waves are actually a combination of these different types of waves. If you're on a boat, you mostly would notice the up and down motion of the transverse part of the wave. However, instead of going just up and down, there is usually more of an elliptical motion to the "rocking" which is brough on by the longitudinal contribution that pushes you back and forth.

For transverse waves, we think about them as oscillations around a median value. The maximum displacement of a wave from the median value is called the amplitude. The distance between identical points on the wave is called the wavelength. The other key feature of a wave is it's period. The period of the wave is the time required for the wave to travel a distance of 1 wavelength, and hence is a measure of the velocity the wave is traveling at. Also, the highest points of the wave are called the "peaks" and the lowest parts of the wave are called the "troughs."

3. Wind is actually the most common cause of waves. Basically, the wind applies a shearing force across the surface of the water that gives you waves (the same thing if you blow across the top of water and see ripples form. Waves can also be formed for geological sources such as offshore earthquakes and volcanic eruptions. Other factors such as underwater currents can also cause waves.

A related phenomeon are the tides, which is the rising and falling of ocean levels. These are primarily determined by the position of the moon and the sun (note that the sun's contribution is about half that of the moon because it is so far away from the earth!). It might be possible that since the earth's orbit is elliptical, the contribution to the tides from the sun will vary with the seasons, but I am not sure how big of an effect that is. In situations where the contribution of the sun and moon to the tides work together and are additive, you get "spring tides," although, I do not believe that they are actually correlated with happening in the spring!

4. I do not have any particular suggestions other than what I have written in parts 1-3, but hopefully that will get you started and on your way. In addition to the "basics" of waves, I would research the different causes of waves to discuss in more detail how waves form and travel. Good luck!

Answer 3:

The kinds of properties of waves a physicist might think about are
the amplitude (height) of the wave, the speed at which it moves, the
distance between one wave and the next, and whether any of the
properties change as the wave travels.

A physicist would like to understand what causes an ocean wave
and how conditions of the atmosphere, the water, and the ocean
floor cause the properties of a wave to change. Some examples:
How does changing the temperature of the ocean, change how
waves move? How does wind speed effect waves? Does it matter
whether the ocean is deep or shallow?

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