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Measuring The Velocity of Sound

published on: 5/7/2009

Contributing Teacher(s): Cathy Green,

Subject Area: Science/Physical,

Grade Range: High School (9-12)

Materials Needed:

• See lesson

Objective:

1. The student will collaborate with other students to design and perform an experiment which will measure the velocity of sound.
2. The student will anticipate sources of error and modify plans to minimize error.
3. The students will collect data and organize it into table form.
4. The students will perform calculations to determine theoretical and experimental values for the velocity of sound.
5. The students will analyze sources of error and communicate using complete sentences.

Essential Question:

Instructional Strategy: Prior Knowledge & Connections

Process Standards: Goal 1.2 conduct research to answer questions and evaluate information and ideas
Goal 1.3 design and conduct field and laboratory investigations to study nature and society
Goal 1.8 organize data, information and ideas into useful forms (including charts, graphs, outlines)

Content Standards: SC7, SC1,

G.L.E.:

Time Allowance: 4 classes required. Day One: Background information. Prelab1. Discuss, brainstorm, and plan strategy. Day 2: Collect data. Day 3: Calculations/data analysis. Day4: Pre-lab and lab2

Technological Resources:
The students are welcome to use internet research as they formulate their plans but they are not required to do so. If they have technical resources at home that will help them measure the speed of sound, they are also welcome to use them. Usually, their technology is very simple but it varies each year.

Extensions:
After analyzing their sources of error, the students may choose to redesign their plan and repeat the experiment to try to improve their data. Another extension would be to have the groups present their experimental design and results to the rest of the groups. This would allow the class to analyze why one process was more successful than another. The class as a whole could generate a new plan that all groups would try then data could be compared and compiled.

Integration:
This process integrates written communication in the experimental design and in the error analysis. The students will use visual communication in their diagram of their plan. They will use math skills and if the extensions are used, they will be responsible for an oral presentation.

Differentiation:
Differentiation is generally an easy issue with this exercise because the students will design an experiment which is appropriate to their skills. Students with hearing impairments may need to supplement with technological aids.

Assessment:

Description: This lesson is used at the beginning of my unit on sound. The students need to have previous knowledge of percent error calculations, data collection, and data organization. I intentionally do not give them very much help with the first lab because I want them to anticipate problems in their experimental design. I also do not make their grade contingent on how well their conclusion agrees with the accepted value because the point of the exercise is to anticipate problems, analyze data, and reflect on the success or lack thereof of their plan. I tell the students they will work in groups of 2 to 3 to design and execute a plan to measure the velocity of sound. We have a brief discussion about why it is difficult to measure and how they can minimize error. It may help to compare how difficult they think it would be to measure the velocity of light compared to the velocity of sound. Do light and sound obey distance equals rate times time? They are welcome to use any materials that I have or they can use materials from home. They must design, describe, and illustrate the plan before any experimentation. They must include at least 8 trials in their data. They must also document the temperature. After collecting data, the students cooperatively calculate average velocity, theoretical velocity and percent error. Then they write an error analysis. The second lab is used to present to the students a way to measure velocity of sound using new physics concepts that they are learning with the closed and open pipes. At the end of both labs, we discuss differences they may have found in experimental error between a procedure that they created as opposed to following a provided procedure.

Comments:

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Classroom Component:

Day one: Present background information and vocabulary. Assign the prelab1 assessment. Students should choose partners and develop strategy and materials list for next time. Give the students the attached "velocity of sound1" prompt and the scoring guide.

For the first lab, the materials needed will depend on the plan generated by the students. They are welcome to use materials that I have such as stopwatches. Anything I do not have, they need to bring from home.

Day two: Students collect data and work on calculations.

For lab 2 they need tuning forks, 40 to 60cm lengths of 1" diameter pvc pipes, rulers, and water containers. I happen to have some giant graduated cylinders that work well but 5 gallon buckets could work or containers could be made from larger diameter pvc.

Day three: Discuss results. Collect lab reports and scoring guides. Present background information for the second experiment and do prelab assessment.

Day four: Collect data and do calculations. This one tends to take less time.

I have 90 minute block classes. An extra day may be needed if you have shorter class periods.

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Pre-Lab Assessment

Name: _________________________________

Vocabulary

Using complete sentences, define the following terms:

1. Frequency-
2. Wavelength-
3. Echo-
4. Experimental value-
5. Theoretical value-

Sample Problems
Required equations: Distance= velocity x time
Velocity = frequency x wavelength
% error = |experimental value – theoretical value|  x 100
theoretical value
velocitysound = 332 m/s + .6( celsius temperature)

1. Two students, attempting to measure the speed of sound, are standing 150m apart. One student used a set of cymbals to generate a sound. It took 0.45s for the second student to hear the cymbals. What was the velocity of the sound waves?

 

2. A single student, attempting to measure the speed of sound, stands 105m from a wall. The student blows a whistle and hears the echo in 0.62s. What is the velocity of the sound?

 

 

3. The temperature of the air for both of these experiments was 25oC.
1. What is the theoretical velocity of sound?
2. What is the percent error for the two experiments?

 

 

 

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Prelab: Velocity of Sound Part II             

Name: _____________________________________

Vocabulary

Using complete sentences, define the following terms:

1. Resonance-

2. Node-

3. Anti-node-

4. Standing wave-

Sample Problems

Required equations: Length = ¼ wavelength
Velocity = frequency x wavelength
% error = |experimental value – theoretical value|  x 100
theoretical value
velocitysound = 332 m/s + .6(Celsius temperature)

1. Using a closed pipe and a tuning fork with a frequency of 512Hz, a point of resonance was measured at 18.5cm. What wavelength produced that sound?

 

 

2. What was the velocity of the sound in problem #1?

 

 

3. If the temperature in the room was 25oC for the experiment in problem #1, what is the theoretical velocity of the sound waves?

 

 

4. Calculate the percent error.

 

 

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Measuring the Velocity of Sound

OBJECTIVE: You and your partner(s) are to measure the velocity of sound as accurately as possible.

As you  know, velocity cannot be measured directly, so you must measure the distance sound travels and how much time it took. Then you may use your data to calculate the velocity of sound. Temperature affects the velocity of sound so be sure to measure that as well. Temperature will not affect your calculations until you are ready for error analysis.

Before you begin, you and your partner need to discuss and agree upon your plan because there are many different ways to do this. Remember that the hard part is that sound goes really fast so you have to figure out a way to deal with that. You also want to minimize error due to delayed human reaction. Have a clear idea of what you plan to do and what equipment you will use before you proceed. You must document at least 8 trials.

FORMULAE:
To find experimental velocity of sound use: Distance = velocity x time
To find the theoretical value use: velocity = 332m/s + .6T where T is temperature in Celcius.
To find the % error use: % error = │experimental - theoretical x 100
theoretical value

TO TURN IN:

1. Paragraph description of your experiment using complete, clear sentences. Include rationales for why you designed your experiment the way you did.
2. Neat, labeled diagram of your experiment.
3. Data table, including straight lines, 8 trials, temperature and all appropriate units.
4. Calculations including formulae, work, answers and labels for average experimental speed, theoretical speed, and percent error. 
5. Error analysis including complete sentences which examine at least 2 different possible error factors.
6. Completed scoring guide.

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Measuring Velocity of Sound with a Closed Pipe                  

Name: _________________________________

Objective: The objective of this lab is to measure the velocity of sound using known qualities of sound produced in a closed pipe.

Safety: For your own safety, do not even think about playing in the water or banging the tuning forks excessively.

Materials: Tall container/bucket for water, tuning forks (high frequencies work best), ruler, thermometer, water, PVC pipe.

Procedure: Obtain the required materials. Fill the water container to within 5cm of the top with water. Hold the top edge of the pipe while submerging most of it in the water. Sound the tuning fork and hold it 1 to 2 cm from the top of the pipe. Move the tuning fork and pipe slowly upward until a point of resonance is found. Measure the distance from the tuning fork to the water level and record distance (L) on the data table in meters. Note additional distances if other points of resonance are found. Repeat steps with 2 other frequencies of tuning forks. Record the room temperature.

Data:     

Trial	F (Hz)	L (m)	Add’l L (m)
1
2
3
Temperature (oC)

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Velocity of Sound Scoring Guide

NAME:___________________________________________________

PARTNERS: ______________________________________________

CRITERIA/ VALUE	EXPERIMENT	DATA	CALCULATIONS	ERROR ANALYSIS
6	Complete sentences, each step has a description and clear rationale, complete illustration included	At least 8 trials documented in table form. Temperature and appropriate units shown.	All work, answers, labels included for average velocity, theoretical velocity, and % error.	Complete sentences used, at least 3 factors examined thoroughly.
4	Fewer than 4 grammatical errors, failed to explain 1 step OR forgot illustration.	6 to 7 trials plus temperature in table form.	1 to 2 slight errors in calculations.	Complete sentences, only 2 factors examined thoroughly.
2	Included 2 out of 3 of the above errors.	4 to 5 trials plus temperature in table form.	3 or more errors in calculations.	Complete sentences, only 1 factor examined.
0	Included 3 out of 3 of the above errors.	Less than 4 trials done.	Calculations don’t agree with data collected.	You didn’t do it!

TOTAL: __________

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