Date: Thu, 04 Dec 1997 22:25:42 -0600 (CST)
From: rahbar@ALPHA.NSULA.EDU
Subject: Re: Vectors
To: Pinhole Listserv <pinhole@exploratorium.edu>
Wait a minute, before you go any farther I need to correct Mr. Marc
Afifi comment about the Eq. PE=mgh.
In this Eq. g is NOT the only vector. If it was then PE (the potential
energy) would be a vector. The true story is that Work= the dot product of
two vectors, namely Force and displacement (W=FDcos(alpha)). As a result
the work is a scalar quantity. And also work = -PE, therefore in the Eq.
PE=mgh, mg is the force, h is the displacement and the angle alpha is
either 0 or 180 deg. depending on the direction of motion. If there is
any questoin, please let me know. A. Rahbar from Louisiana.
On Thu, 4 Dec 1997, Pinhole Listserv wrote:
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 07:00:19 U
> From: blohman@coastside.net
> Subject: AP Science courses
>
> There is a debate at my school concerning the advantages and disadvantages
> of AP science. At present we have only 3 years of science - Biology,
> Chemistry, and Physics. We are considering adding a 4th year but are arguing
> about what it should be. Some feel that AP is not given credit by most
> universities; that it is an expensive course to set up ($15,000 for AP
> Biology??); and that many high schools are moving away from these courses.
> My position is the exact opposite of this. I feel that students need an AP
> course just to be prepared to go into a science major; the AP test and
> credit is secondary.
>
> There are only 4 of us in the department and we are all opinionated and
> prejudiced toward our own views. I would like to get some other opinions,
> does anyone out there have any?
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 09:06:20 U
> From: pauld@exploratorium.edu (Paul Doherty)
> Subject: vector components
>
> Paul,
>
> Had a wild day in class. Some really smart kids could not handle the idea
> that vectors could be broken into components. Specifically, I was using the
> example of an object sliding down an inclined plane. I tried to show how the
> force of gravity could be considered to be two components, one parallel to
> the incline, the other perpendicular to it. The kids kept arguing that
> gravity only pulls straight downward, not at an angle. I've got a few ideas
> for tomorrow. I tried to show them that an object moved down an incline and
> therefore must be experiencing a force and since the only force we can think
> of is gravity, this must be gravity, even if it seems strange. I think they
> need a different way of thinking about this and was wondering if you might
> have a little insight.
>
> Thanks,
> Steve
>
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 09:34:59 U
> From: Steven Eiger <eiger@montana.edu>
> Subject: Re: vector components
>
> How about attaching two or more strings to an object and pulling it in
> different directions, and seeing what direction the object takes. Point
> out that a string can only pull along its length axis. eiger
>
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 09:35:52 U
> From: Steven Eiger <eiger@montana.edu>
> Subject: Re: AP Science courses
>
> My opinion on which AP course to teach would be physics, maybe chem but not
> biology. I also think that a course in human physiology, while not AP is a
> good thing to offer. AP Bio is a rehash of intro bio, and then students
> often need to repeat the same course in college,and then most people go
> into bio fields which are not well covered in that intro course anyway, eg.
> molecular biolgy or medicine. It becomes drudgery in my opinion.
> Meanwhile students entering college are often deficient in problem solving
> skills, reading graphs, using math; the things that physics strengthens in
> spades. Bio is too descriptive at that level and does little towards
> getting analytical thinking in gear. Eiger
>
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 12:20:30 U
> From: karenk@exploratorium.edu (Karen Kalumuck)
> Subject: Re: AP Science courses
>
> Dear pinholers -
>
> Regarding AP science courses - and particularly biology - I'd like
> to submit my opinions for discussion....For those of you who don't know me,
> I conducted research in genetics and molecular biology for 8 years as a
> doctoral student and postdoctoral fellow, and was a college professor in
> Biology for 7 years where I taught a variety of Bio courses, had close
> advisory relationships with students through their entire college career,
> and managed an active research program involving students focusing on the
> physiology of fertilization. I've been the Biologist in the Teacher
> Institue for four years, so have a good familiarity with high school
> biology courses/requirements and the limitations of the classroom. So, I
> do have some experience in this issues at hand.
>
> The largest deficiency I've seen in college students at the
> introductory level is their lack of experience in critical
> thinking/inquiry. They need experience in designing experiments (inquiry)
> including the use of literature searches which leads to an hypothesis, the
> use of positive and negative controls, setting up the experiments, how to
> gather/record data, statistical analysis, interpreting data, etc. Writing
> skills are very good in some of them, highly lacking in others. They need
> to learn to communicate their results (obviously good communication skills
> serve everyone well, not just science majors!) The use of "state of the
> art" equipment in and of itself (ex. PCR, DNA sequencing, etc.) does
> nothing to address these issues. If a student has a firm foundation in
> the scientific process, how to THINK, then they have no problem using state
> of the art equipment. If a student has no idea how to set up an
> experiment, what a control is, or how to interpret data, all the fancy
> equipment in the world won't help them.
>
> I agree with Steve Eiger's statement:
>
> "Meanwhile students entering college are often deficient in problem solving
> >skills, reading graphs, using math; the things that physics strengthens in
> >spades."
>
> Absolutely - physics will strengthen those skills. However, I vehemently
> disagree with his following statement:
>
> "Bio is too descriptive at that level and does little towards
> >getting analytical thinking in gear"
>
> Designed properly and keeping analytical thinking in mind, there are
> countless numbers of projects/experiments which could be tackled in an AP
> Biology lab, in fact, even in an introductory HS bio lab, which would
> address my concerns as well as incorporate math and high level analytical
> skills. (for example, I've been doing workshops for HS teachers on
> nature's patterns, exploring them; to find out why hexagons are so
> prominent in natural forms requires both trigonometry and calculus). I am
> more than happy to share the multitude of activities I have in my stock
> with anyone who is interested. There is a common misperception that Bio is
> only descriptive - and indeed it is often taught that way in HS and even
> college - however with a little thought and creativity it becomes highly
> quantitative - having students design projects,etc. also allows them
> ownership of the project which sparks their interest and enthusiasm.
>
> As far as the statement:
>
> " AP Bio is a rehash of intro bio, and then students
> >often need to repeat the same course in college,and then most people go
> >into bio fields which are not well covered in that intro course anyway, eg.
> >molecular biolgy or medicine. "
>
> No intro college course is going to be able to go in depth in
> EVERYTHING, not just biology, and I can certainly say it depends on the
> college, department and instructor as to what will be emphasized. I
> ALWAYS had my college students in labs, even with 100 students, have some
> latitude in designing and conducting their own experiments as part of the
> course - probably the most valuable experience they had in the course. So
> again, we are back to the need for Critical Thinking and experimental
> design!
>
> I agree with Steve that a human physiology course could be a good
> choice to develop analytical skills in HS students. To be really
> revolutionary, if students have taken Bio, Chem and Physics, why not offer
> an "advanced science" course which incorporates ALL of these - indeed,
> these are not separate fields, as is reflected in much of what we do here
> in TI. The major focus could be students learning the scientific method,
> searching the literature, forming an hypothesis, designing and conducting
> the experiment, gathering/recording data, interpreting results,
> COMMUNICATING their results, doing the next experiment. I'll bet it could
> be done for less than $15,000!!!
>
> Actually, I'd be interested in helping to design such a high school
> course - any takers?
>
> ----Karen Kalumuck
>
>
> Karen E. Kalumuck, Ph.D.
> Exploratorium Teacher Institute
> 3601 Lyon St.
> San Francisco, CA 94123
> 415-561-0313
> karenk@exploratorium.edu
>
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 12:25:20 U
> From: geoff ruth <geoffr@eastside.org>
> Subject: Re: vector components
>
> Wait! I'm confused too -- I'm with your kids. I think that gravity does
> pull only straight down. I think that the reason that the ball (or whatever
> it is on the ramp) is moving at an angle is because the ramp is exerting a
> normal force perpendicular to the surface of the ramp. When you do vector
> addition to combine these two forces, then you get something that points in
> the direction the ball actually moves. Only if you take a coordinate system
> where y (or x) is not parallel to the direction of the force of gravity,
> will you split up the force of gravity into components.
>
> Maybe that's what you actually did in class, is set up a coordinate system
> where x is parallel to the table's surface. If so, then I think that the
> conceptual difficulty might be one that has to do with the idea of
> reference systems and relative coordinates.
>
> Let me know where __my__ confusion lies.
>
> - -Geoff Ruth
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 17:03:21 U
> From: pauld@exploratorium.edu (Paul Doherty)
> Subject: Re: vector components
>
> indeed Gravity is down.
> However, the surface of the inclined plane has a component that is down
> and a component that is horizontal.
> Thus gravity is along the down component of the plane.
>
> Paul D
>
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 17:39:35 U
> From: Gene Thompson <gthompso@ccsf.cc.ca.us>
> Subject: Re: AP Science courses
>
> Designing an advanced level, coordinated or integrated science course?
> When, how, etc, etc, etc...????
>
> Ellen Koivisto
> George Washington High School
> San Francisco
>
>
>
> ----------------------------------------------------------------------
>
> Date: 3 Dec 1997 21:18:04 U
> From: mafifi@redshift.com (Marc Afifi)
> Subject: Re: vector components
>
> Interesting question, though it seems like a question of semantics. Have
> your students concluded that gravity is not responsible for avalanches?
>
> I suggest the following approach.
>
> Ask the students the following questions:
>
> 1. What keeps the object on the plane? Ans. Its weight.
>
> 2. What accelerates the object along the plane? Ans. Its weight.
>
> 3. What gives an object its weight? Ans. Gravity, F=mg
>
>
> Therefore, since mass is not a vector quantity, the only possible
> explanantion for this accelerating force along the plane is that the
> component of its weight which is parallel to the plane is what is producing
> the acceleration of the object along the plane. As the plane's angle of
> inclination increases its acceleration along the plane increases until the
> plane is 90 degrees at which point the acceleration of the object is equal
> to the acceleration due to gravity. What else but gravity could produce
> this effect?
>
> Another way of looking at it is to think in terms of potential energy. The
> object wants to lower its potential energy which is PE=mgh. Again, g is the
> only vector quantity in the equation. Consequently, it seems that we _can_
> think of the acceleration due to gravity as having perpendicular components
> for ease of understanding. Of course, we all know that gravity wants to
> accelerate objects radially toward the center of the Earth but that doesn't
> help us understand the motion of objects down an inclined plane, which gets
> in the way of the radial acceleration. Remember, vectors are just a
> convenient method of analysis...they're not real, and that is perhaps the
> most important lesson here.
>
> - -Marc
>
> ______________________________________________________________________________
> Favorite Oakland Raiders motto: Marc Afifi
> Pacific Grove HS
> Just When Baby? 615 Sunset Dr.
> Pacific Grove, CA 93950
>
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