Homework to be turned in on Tuesday

Please write your work and answers on a sheet of paper that you can turn in.  Thanks!

1.  What factor(s) does the period of a pendulum depend on?

2.  Draw the approximate shape of a graph of period vs. length for a pendulum.

3.  The equation we've seen in class is the period of a "simple" pendulum.  What do you suppose makes our pendulums "simple"?

4.  Calculate the period of a 5-m long pendulum.

5.  If the pendulum in #4 above were taken to Mars, where the gravity is roughly 40% Earth's gravity, how would the period be different (if at all)? 

6.  Consider a 261.6 Hz sound wave (this is approximately the note 'middle C').  Assume that the speed of sound at sea level is 340 m/s.
a.  What is the wavelength of this sound wave? 
b.  Do you think the wavelength of this sound wave would be different on the Moon?

Homework

Hi - some homework for you.

1.  Be able to define these terms:  amplitude, crest, trough, wavelength, frequency, wave speed.

2.  The equation for speed of a wave is:

speed = frequency times wavelength

Write this symbolically.

3.  Solve.  What is the wavelength of a 440 Hz sound wave (speed is 340 m/s)?

Play around with this applet:

http://phet.colorado.edu/sims/wave-on-a-string/wave-on-a-string_en.html

Lab homework

You will be submitting an informal lab report for your pendulum work - this will be submitted individually, 2 classes from now.

In it, you should have:

Graph of Time vs. Length, with a curve fit
Graph of Time vs. Square root of length, with a linear regression line (and slope)
Graph of Time vs. Angle (if you took that data)

On the second graph, the regression line equation IS the equation for your experiment.  Write down that equation and talk (in a conclusion) about how well it compares to the ACTUAL equation for the period/time of a pendulum:

Note that g is a local gravitation constant, equal to around 9.8 m/s/s (that's how quickly gravity makes object accelerate, in m/s per second).  If you work out the constants (2 pi divided by the square root of 9.8), you get a coefficient of around 2.0.  So a local version of the equation becomes:

T = 2 sqrt (L)

In your conclusion (which will be 2-3 paragraphs at minimum), discuss:

- the extent to which your equation resembles the one above
- sources of error in your experiment
- ways to improve your experiment
- anything else you wish to talk about

Finally, answer these 2 questions in your short report:

1.  Knowing the formula above, what is the period of a 3-m long pendulum?  Calculate this.
2.  (This requires some algebra.)  How long should a pendulum be for it to have a 1 second period?

Again, here's what is due in 2 classes:

Graphs
Conclusion
Question to answer

And it should be neat - typed is nice, but handwritten is ok, too.

Also

After you download Logger Pro, play around with it. Bring a graph of your data next class.

Logger Pro download

Logger Pro 3.8.6.1 with sample movies (Windows)

Link: http://www.vernier.com/d/vcwrv

Password: extrapolate

Logger Pro 3.8.6.1 with sample movies (Mac OS X)

Link: http://www.vernier.com/d/kdz9e

Password: extrapolate

The relationship?

You now have some pendulum data.  Examine it and decide which (if any) variables are relevant.  You may find that some are more relevant than others - perhaps some have differences that can be explained by timing issues.

How will you get a relationship out of this data?  What is the best way to formulate a "rule" for your data?  How can you turn your data into a predictive tool?  Would a graph be helpful?

Think about these questions and make a first attempt at formulating a rule.  Bring this to class.  If you are feeling more ambitious, consider how you might make a mathematical tool (equation?) out of your data.

Lab

Our goal will be to determine a relationship that describes the motion of a pendulum - specifically, how the time (for a complete swing - the period) depends on particular variables.  Ideally, we will have a relationship that has predictive ability - something that we can use to predict the period of any theoretical pendulum.

Think about what variables you would test to find out whether or not a pendulum's period is altered (and how)?

Think also about how many trials you may need to take, the range of values (for example, if we're talking about length - how short to how long?) and how you will represent your data (chart, graph, both?).

HW for after Monday's class

http://www.youtube.com/watch?v=NwyeK36Gh-s

Watch as much as you can stand - comment on what makes it believable or NOT believable.

Also, our first lab begins next class.  Think about the following question:

What is a relationship that describes the motion (time) of a pendulum swing?  How can we determine this?  How can we know if our model/relationship/equation is "correct"?

We will spend the next 2-3 classes treating this problem.


https://www.youtube.com/watch?v=2MFAvH8m8aI&feature=player_embedded
If you ever have an hour to kill - the best documentary on pseudoscience ever.

Pseudoscience!

What Is Pseudoscience?
Distinguishing between science and pseudoscience is problematic

By Michael Shermer

Climate deniers are accused of practicing pseudoscience, as are intelligent design creationists, astrologers, UFOlogists, parapsychologists, practitioners of alternative medicine, and often anyone who strays far from the scientific mainstream. The boundary problem between science and pseudoscience, in fact, is notoriously fraught with definitional disagreements because the categories are too broad and fuzzy on the edges, and the term “pseudoscience” is subject to adjectival abuse against any claim one happens to dislike for any reason. In his 2010 book Nonsense on Stilts (University of Chicago Press), philosopher of science Massimo Pigliucci concedes that there is “no litmus test,” because “the boundaries separating science, nonscience, and pseudoscience are much fuzzier and more permeable than Popper (or, for that matter, most scientists) would have us believe.”

It was Karl Popper who first identified what he called “the demarcation problem” of finding a criterion to distinguish between empirical science, such as the successful 1919 test of Einstein’s general theory of relativity, and pseudoscience, such as Freud’s theories, whose adherents sought only confirming evidence while ignoring disconfirming cases. Einstein’s theory might have been falsified had solar-eclipse data not shown the requisite deflection of starlight bent by the sun’s gravitational field. Freud’s theories, however, could never be disproved, because there was no testable hypothesis open to refutability. Thus, Popper famously declared “falsifiability” as the ultimate criterion of demarcation.

The problem is that many sciences are nonfalsifiable, such as string theory, the neuroscience surrounding consciousness, grand economic models and the extraterrestrial hypothesis. On the last, short of searching every planet around every star in every galaxy in the cosmos, can we ever say with certainty that E.T.s do not exist?

Princeton University historian of science Michael D. Gordin adds in his forthcoming book The Pseudoscience Wars (University of Chicago Press, 2012), “No one in the history of the world has ever self-identified as a pseudoscientist. There is no person who wakes up in the morning and thinks to himself, ‘I’ll just head into my pseudolaboratory and perform some pseudoexperiments to try to confirm my pseudotheories with pseudofacts.’” As Gordin documents with detailed examples, “individual scientists (as distinct from the monolithic ‘scientific community’) designate a doctrine a ‘pseudoscience’ only when they perceive themselves to be threatened—not necessarily by the new ideas themselves, but by what those ideas represent about the authority of science, science’s access to resources, or some other broader social trend. If one is not threatened, there is no need to lash out at the perceived pseudoscience; instead, one continues with one’s work and happily ignores the cranks.”

I call creationism “pseudoscience” not because its proponents are doing bad science—they are not doing science at all—but because they threaten science education in America, they breach the wall separating church and state, and they confuse the public about the nature of evolutionary theory and how science is conducted.

Here, perhaps, is a practical criterion for resolving the demarcation problem: the conduct of scientists as reflected in the pragmatic usefulness of an idea. That is, does the revolutionary new idea generate any interest on the part of working scientists for adoption in their research programs, produce any new lines of research, lead to any new discoveries, or influence any existing hypotheses, models, paradigms or world­views? If not, chances are it is pseudoscience.

We can demarcate science from pseudoscience less by what science is and more by what scientists do. Science is a set of methods aimed at testing hypotheses and building theories. If a community of scientists actively adopts a new idea and if that idea then spreads through the field and is incorporated into research that produces useful knowledge reflected in presentations, publications, and especially new lines of inquiry and research, chances are it is science.

>


http://www.randi.org/site/index.php/encyclopedia.html

http://www.quackwatch.com/01QuackeryRelatedTopics/pseudo.html

http://en.wikipedia.org/wiki/Pseudoscience

http://www.skepdic.com/pseudosc.html