First we noted that the intensity of a sound wave (in Watts per square meter) falls off as we move farther from the source of the sound. For a sound wave that expands spherically, the intensity will decrease by a factor of 4 if we double our distance from the sound source. If we increase our disatance by a factor of 5 from the sound source, then the intensity will be only 1/25 as much. We related the idea of the intensity of a sound wave to the sound level, which is measured in decibels, dB: We will address Chapter 12 Problems 9, 10, 11, 12, 16, and 18 on Tuesday.
We presented the solutions to Ch 12 Problems 4, 5, and 7. Problem 5 took a bit of thought and time. Indeed, it is one of those more difficult problems until you get into the problem solving game a bit more. Still, it was a worthy challenge.
We figured out how much time it takes for sound to travel 1 km and 1 mi today. In fact, we took liberty to expand our knowledge of a few other common values, namely how much a pint of water weighs and what a gallon of water (or milk, for that matter) weighs. Next we took a quick look at the speed of sound in materials other than air and noted that sound travels faster in helium than in air and slower in sulfur hexafluoride than in air. The results can be seen in these videos:
Assignment:
Assignment for Friday:
The main event today was the evaluation of our rough drafts of the speed of sound experiment.
Assignment:
We saw how to find the mean value as well as the standard deviation of the speeds of sound that we calculated from our data. In addition, we saw how to calculate the percent difference between our value of the speed of sound and the accepted value.
Assignment for Tuesday: Complete a rough draft of your lab report according to the Lab Report Grading Scheme that you received in class. You should include the Title, Purpose, Procedure (including a labeled diagram), and Data and Analysis. The Conclusion need not be completed by tomorrow; we will discuss that final section tomorrow. You will review your draft with your group and with other groups. The Lab Report final draft will be due on Wednesday. Assignment for Wednesday:
We took data with the goal of determining the speed of sound in air today. A few of us also took data to find the speed of sound in helium.
By the way, the lab report format guidelines can be found here. We will discuss our findings and our report on Monday. The lab report itself will not be due until Wednesday at the earliest. Assignment:
We set the stage for determining the speed of sound using our computers along with a microphone. The task tomorrow is to begin collecting enough data to make an excellent determination of sound's speed.
No further assignment tonight. Lab work tomorrow. In celebration of our mastery of waves, we showed off our expertise on a test.
Assignment:
We reviewed for Wednesday's test today.
Assignment:
We presented our work for Ch 11 P: 36, 37, 52, 55, 56, 57 and also for our "Wavelength, Period, Speed" problems.
Our Ch 11 Exam is on Wednesday. Review:
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Physics IIMr. Swackhamer Archives
May 2019
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