Waves Lab

Waves Lab Maria Turner 7B December 15, 2010

I. GUIDING QUESTION/S (State the guiding question/s): Does the flexibility of the medium affect the amplitude?

II.HYPOTHESIS: We think that it will, because for example if you have a slinky, it is a lot more flexible than a piece of string. The metal tends to go farther than the plastic or string, which is what I’m guessing.

III. Exploration (PLAN & DO A TEST):

Manipulated variable: medium (solids).
Responding variable: wave - flexibility

Materials(in order of most flexible to least flexible):
long slinky
big slinky

big rope

yellow plastic pipe

PROCEDURE:

1. Order all of the mediums in order of flexibility.

2. Take the first medium. Have two people create waves using the medium within a measured distance. You, or the third person, should measure the wavelength of each wave and also figure out what the frequency is. Record these, and them multiply them by each other in order to find the speed of the wave. Do the same for all of the mediums.

3. Analyze – does the wavelength, frequency, or speed change according to their flexibility?

IV. RECORD & ANALYZE

DATA:

LONG SLINKY:
Wavelength: 75 cm (20 cm to 80 cm)
Frequency: 3 waves per second
Speed: 225 cm/s
BIG SLINKY:
Wavelength: 320 cm
Frequency: 2 waves per second
Speed 640 cm/s
BIG ROPE:
Wavelength: 102 cm
Frequency: 2 waves per second
Speed: 204 cm/s
YELLOW PIPE:
Wavelength: 98 cm
Frequency: 1 wave per second
Speed: 98 cm/s

Analysis of Data: What happened? Do you see any
patterns? Do you believe that your data
shows accuracy and precision?
The flexibility of the medium doesn’t really seem to affect the wavelength at all. The long slinky has a really small wavelength, but the big slinky has a really big wavelength. This may have some relation to the frequency, which does seem to follow a pattern. However, it may be just a coincidence that the frequency follows a pattern according to the flexibility, so if I were doing a more detailed lab I would test out each material several times and find the average, to make sure that it’s not a coincidence that the more flexible, the more frequent the waves are. I think that because the wavelength didn’t depend on the flexibility, which means that the speed doesn’t really depend on the flexibility either (because wavelength and frequency are both factors of the speed). And, because of that, the amplitude doesn’t end up depending on the flexibility. The only thing that does is the frequency!

IV. Concept Acquisition (CONCLUSION): State the guiding question.
Present the relevant experimental results. Discuss the
relationship between variables. What can you conclude?
Was your prediction correct? If yes, explain. If no,
explain what you understand now about this investigation
and how it taught you something new.

The guiding question was “does the flexibility of the medium affect the amplitude of the wave?” I think that this lab was a very interesting one to do because the amplitude of the wave can include a lot of things. It basically just describes however a medium is disturbed. The wavelength and the frequency multiplied by each other equal the speed, and all three of those factors combined describe the amplitude. It’s interesting to see how if you change just one variable (in this case, the flexibility), then the whole answer changes. My prediction actually wasn’t that specific to the question – I just described the amplitude in general and the results showed that it was really different for each thing describing the amplitude – the wavelength, the frequency, and the speed.

V. Concept Application (FURTHER INQUIRY): Examine the validity of
your data and infer what you think the major causes of
error may have been. Propose methods of improvement. For
example, what modifications did you need to make or would
make next time? Whatever happens in a test, think about all
the reasons for your results. Sometimes this thinking
leads to a new hypothesis. Write down these new hypotheses
(predictions) or inquiries (questions) you may have here in
this section.

What I would want to do if I were to continue this lab is that I would want to try each factor as the manipulating variable – change the wavelength, but not change anything else. Change the medium, but not change anything else, and so on. I think that what could have been improved were the measurements – I’m not sure that they were correct, because some of the data doesn’t really make that much sense to me. If I had tried it a couple of times and then found the average, it would have probably have made for a better analysis.