Mechanical Waves and Sound UNIT PACKET

Student:

Mr. Khalilian

AP Physics

Due Date:

Mechanical Waves and Sound UNIT PACKET

Includes Guides for Notes, HW, and CW

UNIT 8 AGENDA

____ Day 1: Introduction to Mechanical Waves and Sound

· Pre-HW: Read the Mechanical Waves Lab Background and complete the pre-lab questions (p. 4-6)

· Mechanical Wave Intro Lab (p. 7-8)

· HW: Read text 15.1-15.2 and take notes using guide (p. 3)

____ Day 2: The Basics of Mechanical Waves and Sound

· Read Text 15.3 – 16.2 and take notes using note guide (p. 3); when finished, check your notes

· Begin Behavior of 1-D Waves (p. 9-11)

· HW: Finish reading if you did not finish in class (all notes and Behavior of 1-D waves due Monday)

__3/13__ Day 3: The Basics of Mechanical Waves and Sound

· Finish Behavior of 1-D Waves (p. 9-11)

· Read Text 16.3 – 16.7 and take notes using the note guide (p. 3); when finished, check your notes

· HW: All notes and Behavior of 1-D waves due Monday

___3/16_ Day 4: Standing Waves

· Four in Five, p. 24

· Standing Waves on Strings (p. 12) and in Pipes (p. 13-14)

· HW: Multiple Choice #1-3, on a separate sheet of paper with explanations (p. 20)

__3/17__ Day 5: Standing Waves Practice

· Standing Waves Practice Problems (p. 15-16)

· HW: Finish Standing Waves Practice Problems; Multiple Choice #4-6, on a separate sheet of paper with explanations (p. 20)

__3/18__ Day 6: Practical Applications of Waves

· Practical Applications of Waves (p. 17)

· Multiple Choice #7-12 (p. 20-21)

· HW: 1995B6 (p. 22)

__3/19__ Day 7: General Waves Practice/ Begin Musical Instruments

· Four in Five, p. 25

· 1998B5 (p. 23)

· HW: Musical Instrument

__3/20__ Day 8: Musical Instruments Work

· HW: Create Musical Instrument/Practice Performance

__3/23__ Day 9: Musical Instruments Performances

Recommended Book Problems for the Unit: p. 495: 1, 3, 5; p. 496: 9, 11, 13, 15, 23; p. 525: 1, 5, 7, 9; p. 526: 11, 13, 23

NOTES OUTLINE

Notes for this unit should be taken in your notebook. You may use either Cornell or Outline style, but only Outline is presented below. However, instead of giving you where to stop and summarize, you have just been given the headers to set up your notes.

Hint #1: Focus on the vocabulary. Know what each term means, and, if it has a symbol, what it stands for.

Hint #2: The ONLY equation you will really need is the Fundamental Relationship for Sinusoidal Waves.

15.1: The Wave Model
Intro Paragraph
Mechanical Waves
Electromagnetic and Matter Waves à SKIP
Transverse and Longitudinal Waves
15.2: Traveling Waves
Waves on a String
Sound Waves
Wave Speed is a Property of the Medium
15.3: Graphical and Mathematical Descriptions of Waves
Snapshot and History Graphs
Sinusoidal Waves
The Fundamental Relationship for Sinusoidal Waves
15.4: Sound and Light Waves
Sound Waves
Light and Other Electromagnetic Waves à SKIP
15.5: Energy and Intensity à SKIP
15.6: Loudness of Sound
Intro
The Decibel Scale
15.7: The Doppler Effect and Shock Waves
Sound Waves from a Moving Source
A Stationary Source and a Moving Observer
The Doppler Effect for Light Waves
Frequency Shirt on Reflection from a Moving Object à SKIP
Shock Waves
16.1: The Principle of Superposition
Intro
Constructive and Destructive Interference
16.2: Standing Waves
Superposition Creates a Standing Wave
Nodes and Antinodes
16.3: Standing Waves on a String
Reflections
Creating a Standing Wave
The Fundamental and the Higher Harmonics
Stringed Musical Instruments
Standing Electromagnetic Waves à SKIP
16.4: Standing Sound Waves
Intro
Wind Instruments
16.5: Speech and Hearing à SKIP
16.6: The Interference of Waves from Two Sources à Read but no notes necessary
16.7: Beats

Pre-Lab Questions:

1. Compare and contrast transverse and longitudinal waves.

______

2. A fishing bobber floating on the water bobs up and down and back to a point of equilibrium once every 1.2 seconds.

a. Explain what type of wave is causing the bobber to move up and down.

______

b. What is the frequency of the water wave?

______

c. What is the period of the wave?

______

3. Refer to the diagram below in which the vertical distance from the highest point on the wave to the lowest point represents 0.1 m, and the horizontal distance from one letter to the next is 0.05 m.

a. What is the amplitude of the wave?

b. Describe the wavelength in terms of letter intervals. What distance does this represent (in meters)?

c. If the wave travels from point A to point G in 4.5 seconds, what is the speed of the wave?

d. Determine the period of the wave described above.

e. Calculate the frequency of the wave.

Safety Notes

Take care not to suddenly release a stretched Slinky. Always hold a stretched Slinky carefully. Otherwise, the spring may snap back rapidly, which may cause personal injury or damage to the Slinky. Do not extend the Slinky more than 4 meters.

MECHANICAL WAVES LAB

Note: Most of your evidence today will be observational. Feel free to sketch pictures or describe with words. Use the background reading or textbook reading to find the reasoning.

1. Claim: For a transverse wave, the wave carries the material from one end to the other as it moves. (Hint: tie a string to a portion of the slinky and watch what happens to the string.)

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

2. Claim: For a transverse wave, the more energy put into the wave, the faster it will travel.

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

3. Claim: For a transverse wave, the wave stops when it reaches the end of the Slinky.

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

4. Claim: For a longitudinal wave, the wave carries the material from one end to the other as it moves. (Hint: tie a string to a portion of the slinky and watch what happens to the string.)

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

5. Claim: For a longitudinal wave, the more energy put into the wave, the faster it will travel.

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

6. Claim: For a longitudinal wave, the wave stops when it reaches the end of the Slinky.

a. Valid or Invalid? ______

b. Evidence:

c. Reasoning:

______

7. How can you create a standing wave with an antinode?

BEHAVIOR OF 1-D WAVES

A long rope rests on the floor. Its far end is firmly attached to a wall. The stick figure at the left gives the rope a brief, horizontal shake, sending a disturbance, or pulse, along the rope toward the wall. In the diagram, points A, B, C, D, and E are equidistant. Point E is at the wall.

All waves have a source that initiates the disturbance. Except for electromagnetic waves (like radio, microwaves, light etc.), waves have a medium through which they travel. All waves transmit energy away from the source.

1. What is the source of the wave in the rope?

2. What is the medium of transmission of the pulse?

3. Is this pulse a transverse or longitudinal wave? Why?

4. The speed at which the wave travels on the rope is 2.0 m/s. The distance between A and B, B and C, C and D, and D and E is 2.0 meters. Let’s call time zero when the pulse is centered on A (see diagram below).

a. In 2.0 seconds after the picture shown above, where will the pulse be centered?

b. Draw the appearance of the pulse at that moment.

c. Where will the pulse be centered 3.0 seconds after the picture shown above?

d. When pulses strike solid barriers, they reflect on the opposite side of the medium. Where will the pulse be centered 7.0 seconds from the picture above? Draw the appearance of the rope at that moment.

e. Repeat question 4d if the rope is not fixed to the wall. When pulses reflect from a “free” end, they return on the same side of the medium.

5. Next we have two new pictures of a wave traveling from medium W to medium Z. (Square waves are drawn for simplicity.) The energy of the original wave is partly transmitted to Z and partly reflected back into W. See Figures C and D below.

a. There are two ways we can recognize that waves travel faster in Z than in W. Using Figures C and D, explain what they are.

b. There is one feature in these diagrams that suggests that medium Z is not nearly as dense as medium W. Explain.

c. Why is the reflected pulse in medium W smaller than the original pulse in medium W?

6. The pictures below show two pulses on the same medium moving toward each other. Draw the appearance of the medium at the instant when the centers of the pulses overlap at point X. The first question has been completed for you.

STANDING WAVES ON STRINGS

You have a string, and both ends are fixed. String has length L, and the speed of waves is v= FTm/L.

Points of NO oscillation are called = ______

Points of MAXIMUM oscillation are called = ______

General Equations

STANDING WAVES IN PIPES (open pipes)

General Equations

STANDING WAVES IN PIPES (closed pipes)

General Equations

STANDING WAVES PRACTICE PROBLEMS

1. The tension in a particular string is 5.0 N, and the density (m/L) of that string is 0.0004 kg/m. What is the speed of waves on that string?

2. You are given a piece of string of density 0.00036 kg/m. You need waves which travel at a speed of 100 m/s on the string. What should the tension in the string be?

3. A standing wave with a fundamental frequency 125 Hz is set up in a string which is 2.5 m long.

a. What is the speed of the waves on this string?

b. What is the frequency of the…

i. first harmonic?

ii. second harmonic?

iii. third harmonic?

4. What are the frequencies of the first four harmonics in a pipe of length 75 cm if the pipe is:

a. open at both ends? Assume the temperature of air is 20°C.

b. closed at one end? Assume the temperature of air is 20°C.

5. An open organ pipe is designed to produce a frequency of 440 Hz at a temperature of 20°C. By what percent is the frequency increased or decreased if the temperature of the air is 15°C?

6. A 2.0 m long air column is open at both ends. The frequency of a certain harmonic is 410 Hz, and the frequency of the next higher harmonic is 492 Hz. Determine the speed of sound of air in the column.

7. A flute is designed so that it plays a frequency of 261.6 Hz, middle C, when all the holes are covered and the temperature is 20°C.

a. Consider the flute to be open at both ends and find its length, assuming that the middle C frequency is the fundamental.

b. A second player, nearby in a colder room, also attempts to play middle C on an identical flute. A beat frequency of 3 beats per second is heard. What is the temperature of the room?

PRACTICAL APPLICATIONS OF WAVES

1. When a person inhales helium, why does his or her voice mimic a cartoon?

2. How can you tell if an ambulance is moving toward you or away from you?

3. If guitar strings are all the same length, why do they make different notes?

4. How do pianos create different notes?

5. How do flutes create different notes?

6. How can we tell that the universe is expanding?

Due Date:
March 23rd, 2015 in class / Student Name:
Course Name: AP Physics
Period: 3
Teacher Name: Ms. Elbein
Assignment Title: / Build a(n) (Insert name of Musical Instrument Here)
Assignment Summary: / Your job is to use what you have learned about waves, specifically sound waves and standing waves, to build a musical instrument. Your instrument may be a stringed instrument or a wind instrument. Your instrument must play a full octave scale and be in tune. Mr. Redick will (hopefully) come to your performance to hear if your instrument is in tune.
There will be no write-up, only your performance. You must play an entire octave and then perform one short song. You may use a note sheet for your performance.
You may choose your own performance song. It must have a tune though. Please, no Sondheim.
Materials / · You must purchase your own materials. However, you should not be spending a lot of money on this. Decide what you want. If you aren’t sure where to find something, let Ms. Elbein know. If cost is an issue, let Ms. Elbein know (or let your advisor know to let Ms. Elbein know).
· Some recommended materials are: pipes (of any variety), straws, string, wooden boards, etc. Be creative. What can you make a pipe out of?
Procedure and Helpful Hints: / 1. Figure out what an octave is and what frequencies each of your notes should be at.
2. Figure out what length your pipes/strings/whatever need to be. Or where your holes should be cut.
3. Make the instrument.
4. Tune the instrument.
5. Find a song that is one-octave only and less than a minute long. Prepare yourself. Practice.
Rubric / ______Instrument played full octave (20 pts)
______Instrument was in tune (20 pts)
______Scholar played full song (10 pts)
______Scholar demonstrates knowledge of why sounds were created and is able to use vocabulary comfortably and correctly (50 pts)

MECHANICAL WAVES AND SOUND PRACTICE AND REVIEW

1. A string is firmly attached at both ends. When a frequency of
60 Hz is applied, the string vibrates in the standing wave pattern shown. Assume the tension in the string and its mass per unit length do not change. Which of the following frequencies could NOT also produce a standing wave pattern in the string?