Welcome to Physics!

In our first couple of classes we will talk about what science is and what it is not.  In preparation for that, please read this article and, if you have time, follow some of the links below.


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.

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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

Projectile fun.

http://www.walter-fendt.de/ph14e/projectile.htm

Play with this and see how your own problems (and calculations) compare to what the applet gives you.

Forget about Angry Birds - this is the real physics!

homework

practice

1.  A soccer ball is kicked at a 40 degree angle with speed of 22 m/s.  Find:

a.  initial components of velocity
b.  time to apogee
c.  total time in air
d.  maximum horizontal displacement
e.  maximum height achieved
f.  If this projectile had been kicked at this angle/speed off a 20-m high cliff, how would the problem change?  You don't have to solve it, but think about how it could be dealt with.

2.  Look up the range equation - it is a useful expression for solving projectile motion problems when trying to determine the maximum horizontal displacement.  When is it useful?

some new problems

These are assigned first for E-block.  Then C-block will have a go at them after Monday's class.

1.  Projectile motion.  Consider throwing a ball horizontally at 30 m/s off a 25-m high cliff.

a.  Find the time to hit the ground.
b.  Find the horizontal distance where the ball lands from the cliff.

2.  Consider a velocity vector of 40 m/s, at an angle of 60 degrees (with respect to horizontal).

a.  Find the x-component (horizontal).
b.  Find the y-component (vertical).

This type of thing will be important when we deal with projectiles launched at angles.

3.  Think about how we might approach the problem of projectiles launched at angles.

For example, if you threw a ball at 20 m/s, with an angle of 30 degrees, how would you find things like the time in air and horizontal displacement?  Try this, or think about how to approach it.

4.  Practice for vectors at non-right angles.  Two vectors, 200 and 500, are separated by an angle of 40 degrees.  Find the resultant vector (c, if you use the law of cosines).

vector hw

The following problems involve vector addition.

1.  You're on a people mover, which itself is moving 3 m/s to the right.

a.  If you run at 2 m/s to the right, what will be your speed relative to an outside observer not on the people mover?

b.  How should you move to "stay in place?"

c.  If you run at 4 m/s to the left, what will be your speed relative to an outside observer not on the people mover?


2.  Two ropes are attached to a large boulder.  One rope is being pulled with a 50 lb force to the East.  Another rope is being pulled with a 75 lb force South.

a.  What is the net force on the boulder?

b.  What angle does this net force make with respect to East?


*3.  A small airplane is flying due SouthEast at 70 m/s.  It is hit by a wind (15 m/s, due South).

a.  Draw this problem.

b.  Assuming that these vectors add concurrently (same place, same time), what will be the resultant vector - magnitude and angle.  You may need to use the law of cosines and/or law of sines.


*4.  Consider a 100 lb force vector, at an angle of 30-degrees with respect to horizontal.  What part of this vector can be considered to be horizontal and what part is vertical?  This is a little tricky, breaking a vector into components.  Make a triangle and set up sin and cos relationships for the vector/triangle.


* these are a wee bit tricky.  Do try them, though.

trig practice

...for those who want/need it.

1.  Consider a 5-12-13 right triangle.  Find the angles.

2.  A right triangle has a 5-m long hypotenuse.  One angle in the triangle is 20 degrees.
Find the other sides.

3.  A "river problem."  A toy motorboat heads south across a 20-m stream.  The current
in the stream is flowing at 2 m/s toward the west.

a.  Draw this problem.
b.  Find the time to cross the stream.
c.  Determine where the boat lands.


ALSO - DON'T FORGET THAT THE MOTION QUIZ IS DUE AT THE BEGINNING OF THE NEXT CLASS.