 Chapter 17 Mechanical Waves & Sound. How does a disturbance produce waves?  Procedure  Fill a clear plastic container with water.  Observe the surface.

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 Chapter 17 Mechanical Waves & Sound

How does a disturbance produce waves?  Procedure  Fill a clear plastic container with water.  Observe the surface of the water by looking down at an angle to the container. Use the pipet to release a drop of water from a height of 3 cm above the surface of the water.  Repeat Step 2 with a drop released from each of these heights: 10, 20, 50, 60, 70, 90 cm. Create a table to record your observations after each drop.  These observations will be QUALITATIVE (or descriptive, and not mumeric)

Analysis Questions  Which drop produced the highest wave?  Write a general statement (or conclusion) about how the distance a drop falls affects the wave produced in the container.  Using your knowledge of energy, conservation of energy, and energy transfer, explain why the distance a drop falls affects the height of the wave produced. Thoroughly explain your answer.

 Mechanical Waves 17.1 Notes

Inquiry Activity  How does a disturbance produce waves?  P 499  Complete activity, answer questions as a group  Submit one paper per group with all observations recorded and questions answered!

What are mechanical waves?  Mechanical Wave  A disturbance in matter that carries energy from one place to another  Require a medium (or matter) in order to carry energy  All waves carry energy!

What is a Medium?  The material through which a wave travels  Can be a solid, a liquid or a gas  Space is NOT a medium  Why?

How are mechanical waves created?  A source of energy causes a vibration to travel through a medium

Types of Mechanical Waves Transverse  Medium moves perpendicularly (or at right angles to the direction the wave travels) Longitudinal (Compressional)  Medium moves parallel to the direction the wave travels

Transverse Waves Demos  Rope (with ribbon attached)  Student line (arms over shoulders)

Parts of a Transverse Wave Crest  Highest point of the wave Trough  Lowest point of the wave

Compressional Wave Demos  Slinkys!  Hip Bump

Parts of a Compressional Wave Compression  Area where the particles in a medium are spaced close together Rarefaction  An area where the particles in a medium are spread out

Waves transfer ENERGY!  Waves DO NOT transfer MATTER  Waves ONLY transfer ENERGY  Example: THE HUMAN WAVE

Surface Waves  A wave that travels along a surface that separates two media (or two types of matter)  An object resting on a surface wave will move up and down, and back and forth  These two motions result in a circular motion for the object

Wave Animation  http://njscuba.net/biology/misc_waves_w eather.html http://njscuba.net/biology/misc_waves_w eather.html

Breaking Waves

Exit Exercise  With your group, make a Venn Diagram that compares and contrast Transverse and Compressional Waves.

 Properties of Mechanical Waves 17.2

Periodic Motion  Any motion that repeats at regular time intervals  Period  The time required for one cycle, a complete motion that returns to its starting point

Wavelength  Distance between a point on one wave and the same point on the next cycle of the wave  Between adjacent Crests (or troughs), or compressions (or rarefactions)

 One Wavelength One complete wave cycle

Frequency  A periodic motion has a frequency  Frequency  The number of complete cycles in a given time  For waves, this is the number of wave cycles that pass a point in a given time  Measured in cycles per second, or Hertz (Hz)

Frequency & Wavelength  As frequency increases, what happens to wavelength?  Use the slinky at your table to determine the answer to this question, then respond using Socrative  HINT: You can make either TRANSVERSE, or COMPRESSIONAL waves with your slinky

Frequency Formula Frequency = 1 *Remember, period is the amount of time it takes for a wave to complete one full cycle period

Socrative Graph #1

Socrative Graph #2 t in seconds

Socrative Questions…  Two calculating frequency/ period questions

Surfing  Science of Surf - Episode 1 Science of Surf - Episode 1

Wave Speed  REMEMBER  v = d/t  Think of one wavelength as DISTANCE  Thin of period and TIME  Wave Speed = wavelength / period  OR Wave Speed = wavelength x frequency

Wave Speed Example  One end of a rope is vibrated to produce a wave with a wavelength of 0.25 meters. The frequency of the wave is 3.0 Hertz. What is the speed of the wave?  FORMULA  Speed = Wavelength x Frequency

Socrative Practice  Wave Speed Questions

Amplitude  The maximum displacement of the medium from its rest position  The more energy a wave has, the greater its amplitude

 http://www2.biglobe.ne.jp/~norimari/scie nce/JavaEd/e-wave2.html http://www2.biglobe.ne.jp/~norimari/scie nce/JavaEd/e-wave2.html  http://www.sciencejoywagon.com/physics zone/09waves/ http://www.sciencejoywagon.com/physics zone/09waves/

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