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| SCI 580 Science & Children Syllabus & Class Notes |
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Kip Ault, Ph.D., Instructor Lewis & Clark College Box 14 503.768.6106 office |
Class Times
Section 580-02: Mondays & Wednesdays, 9:00 a.m. to 11:30 a.m.,
Bio-Psych Yellow Lab (main campus)
Friday, July 10, 8:00 a.m. to 5:00 p.m. (Oregon Zoo)Section 580-12: Mondays & Wednesdays, 12:30 p.m. to 3:00 p.m.,
Bio-Psych Yellow Lab
Friday, July 10, 8:00 a.m. to 5:00 p.m. (Oregon Zoo)Section 580-22: Tuesdays & Thursdays, 8:00 a.m. to 10:30 a.m.,
Bio-Psych Yellow Lab
Friday, July 10, 8:00 a.m. to 5:00 p.m. (Oregon Zoo)
Catalogue Description
Investigations with everyday materials and common creatures that will enrich teaching in the primary through intermediate elementary years. Participants examine their own, as well as children's, intuitive science notions. The course fosters confidence in teaching hands-on science by attending to teacher understanding of background knowledge and safe, successful use of classroom science equipment.
SCI 580 stresses the availability, utility, and significance of using simple materials found in everyday environments in the conduct of investigations by children. Framed by the concerns addressed in the National Science Education Standards (NSES), SCI 580 approaches science as a topic important to all students with the concept of inquiry having central importance.
Course readings
Carin, A.A., Bass, J.E., & Contant, T.L. (2009). Activities for Teaching Science as Inquiry. Upper Saddle River, NJ: Pearson Merrill Prentice Hall.
Gallas, K. (1995). Talking Their Way Into Science. New York, NY: Teachers College Press.
Kwan, T., Texley, J. & Stoops, E. (2002). Exploring Science Safely. Washington, DC: NSTA.
Objectives
Experience inquiry style early childhood and elementary science curricula in the context of specific topics of study aligned with national and state curriculum standards.
Examine the importance of “talking science” in the context of exploration of phenomena as well as the design of investigations.
Develop the skill of using discrepant events to create interest in natural phenomena.
Practice phrasing questions that sustain inquiry and interest as well as promote thinking.
Help children plan and design investigations with attention to the role of variables.
Infer what children actually understand about natural phenomena from their language and actions.
Schedule
1. June 22/23. Luz y lapiz; Emile’s Broken Twig and Alice’s Looking Glass; the White Whale and the Red Tomato (literature, metaphysics, metaphor, whimsy, and children’s science?)
Read for the next class:
Carin, et al., 92-109, “Light.”
“Looking Crazy” in the class notes.
Jean D. Harlan & Mary S. Rivkin. (1996). “Light,” Chapter 15 of Science Experiences for the Early Childhood Years, 6th Edition. Englewood Cliffs, NJ: Prentice Hall. In the class notes.
Joanne K. Olson. (2008). “Concept-Focused Teaching.” Science & Children, 46 (4), Dec., in the class notes.
S. Rená Smith & Sandra K. Abell. (2008). “Using Analogies in Elementary Science.” Science & Children, 46 (4), Dec., in the class notes.
2. June 24/25. Colored Shadows and Mixing Light (ESS Optics); Milky Dawn and Light Talks. Productive questions schema from Wynne Harlen.
Due next two classes (1/2 of class each day):
Prepare to share a Physical Science Activity with a small group of peers. Use Carin, et al., as a source. Always consult Exploring Safely!
Read for next class:
Kwan, et al., Exploring Science Safely, Chapters 1-4, 6 and 8.
Wynne Harlen and Joel Elstgeest thoughts on “productive questions” from Primary Science: Taking the Plunge (Oxford, UK: Heineman, 1985) in the class notes.
Anna Botsford Comstock and “An Example of Productive Questions” from her classic Handbook of Nature Study (1911) in the class notes.
Gloria Ladson-Billings, “I Used to Love Science . . . and Then I Went to School,” Foreword to Teaching Science to Every Child: Using Culture as a Starting Point,J. Settlage and S.A. Southerland, New York: Routledge, 2007, pp. xiii-xix, in the class notes.
If interested and for a bit of explanatory background (and closure) on optics see the Heron, mirror, and lens figures excerpted from various texts for the class notes.
3. June 29/30. Puzzling Events in Physical Science. Peer Presentations (physical science) Part I; making the familiar unfamiliar and vice versa.
Read for next class:
Gallas, Introduction and Chapter 1, “What is Science?”
Gallas, Chapter 2, “Science Talks: An Overview.”
Gallas, Chapter 3, “Anatomy of a Science Talk.”
“Science Talks: Mapping the Landscape of Imagination” guidelines for evaluating a Science Talk in the class notes.
Hawkins, D., (1965). “Messing About in Science” in the class notes.
4. July 1/2. Peer Presentations (physical science) Part II. Messing about and the learning cycle.
Read for next class:
Gallas, Chapter 4, “Theory Building as an Irrational Activity.”
“Swing Thing” in the class notes.
Carin, et al., 61-61, “What is a Pendulum?”
Kwan, et al., Exploring Science Safely, Chapters 5 and 10.
Science Inquiry Scoring Guide (State of Oregon) in the class notes
5. July 6/7. Pendulums: Variables in Experimental Designs; Science as Process & Science as Theorizing.
Read for next class:
Gallas, Chapter 5, “When the Question is Too Hard.”
Gallas, Chapter 6, “Misconceptions as a Search for Origins.”
Kwan, et al., Exploring Science Safely, Chapters 7 and 9.
Carin, et al., 120-136, “Electricity.”
“A Few Comments about Electrical Force and Energy” in the class notes.
6. July 8/9. Batteries, circuits, and bulbs: Learning key concepts (conductors and non-conductors, parallel and series circuit, etc.).
Read for next class:
“Zoo Tour” in the class notes (p. 41).
Shepherson, D. (1992). “Environmental Enrichment” in the class notes.
“Artistry and Science at the Oregon Zoo” in the class notes.
Josie Glausiusz. (2001). “All in the Whale Family.” Discover in the class notes.
“Compromised Survivorship in Zoo Elephants.” Ros Clubb, Marcus Rowcliffe, Phyllis Lee, Khyne U. Mar, Cynthia Moss, and Georgia J. Mason. Science, 12 December 2008 322: 1649 [DOI: 10.1126/science.1164298] (in Brevia). Accessed on-line, January 8, 2009. In the class notes.
7. July 10. Artistry and Science at the Oregon Zoo.
Due next two classes:
Prepare to share a Life or Earth/Space Science Activity/Inquiry with a small group of peers. Use Carin, et al., as a source. Always consult Exploring Safely! I invite you to draw upon resources for teaching science using pillbugs (see “Meet the Pillbugs” in the class notes)—perhaps several persons will collaborate to organize pillbug investigations.
Read for next class:
Gallas, Chapter 7, “Science Talk for Synthesis.”
Gallas, Chapter 8, “Building Curriculum from Children’s Questions”
“Meet the Pillbugs!” in the class notes. Keep in mind that they may be deep in rotting wood at this time of year and a bit difficult to find.
Burnett, The Pillbug Project in the class notes.
“The Behavior of Woodlice,” Activity 17 from Thinking Science by Shayer and Adey, in the class notes.
http://www.growwithholden.org/Lesson_Plans_Pillbug.htm
http://www.udel.edu/msmith/pillbugs.html (You will find a host websites if you search for information and exercises using pillbugs or “isopods.”)
8. July 13/14. Peer Presentations of (life or earth/space science) Part I. Designing investigations.
Read for next week:
Gallas, Chapter 8, “Building Curriculum from Children’s Questions”
Settlage & Southerland, “Chapter 14: Teachers Negotiating Different Communities,” pp. 347-374, in Teaching Science to Every Child in the class notes.
9. July 15/16 Peer Presentations (life or earth/space science). Meet the Pillbugs: Symposia and science talks.
Assignments
1. Class Newsletter. Working with a partner, keep notes for a class and then present them the following class, creatively published for all to enjoy. We will use the newsletter to revisit the previous class and bring closure to unanswered questions.
2. Physical and Life/Earth Science Activity/Inquiry: Present to your peers an interesting science activity (use Carin as a principle source). Frame the presentation with questions that prompt interest and sustain inquiry. Be certain to test your materials before sharing them with your peers. Prepare an outline to share (electronic is OK) with the class that has:
i. An objective for student learning.
ii. The task, puzzle, problem, or question that invites engagement.
iii. A list of “productive questions” (commit to prediction to start).
iv. “How it works” in your own words.
v. Source.
Guidelines for conducting your activity:
1. Start with Safety Concerns. Consult Exploring Safely by Kwan and Texley.
2. Choose your activity from the Carin, et al., resource book. If from another source, please bring the directions/reference to distribute in class.
3. If possible, try out your Activity at your school.
4. Expect support from you classmate audience.
5. DO NOT prepare a lecture explaining the phenomenon.
6. DO try to begin with a question that requires your audience to commit to a prediction or focus on something puzzling and unexpected. For example, try to phrase questions in the form, “What do you think will happen when . . . .?” rather than “Why does _____ occur/not occur?”
7. Direct attention to what happens by asking numerous questions that call for noticing and describing the event. These are questions that have answers easily found by observing closely.
8. Ask questions that call upon members of the audience to clarify their ideas.
9. Ask questions that call upon your audience to make simple inferences, prompted by a review of observations.
10. Refrain from asking intimidating “why” (or explanatory) questions unless you have established momentum toward their resolution.
11. As you near the end of your presentation, solicit several plausible explanations or multiple answers to a key question. Accept all hypotheses as reasonable. Your role is to encourage contributions of plausible, competing, clearly expressed ideas.
12. See if you can prompt a Science Talk about the phenomena of interest—a phase where you step back and the group “theorizes,” based upon each other’s thinking.
Audience Role. When you are not presenting, you are still active. First, you are learning science. Secondly, you are a source of feedback to the presenter about his or her questioning skills. Record observations, take notes, and make sketches as appropriate to the exercise. For example, write down predictions when prompted to do so. Secondly, keep track of your own questions as they arise. Finally, write down several examples of “productive questions” posed by the presenter. Refer to this list of questions at the end when the group provides feedback to the presenter.
Grading:
1. Exemplary performance (“credit”):
· Serious reflection, clear expression, and careful organization always evident.
· Careful attention to phrasing productive questions and encouraging conversation that respects students at all levels of understanding.
2. Unacceptable performance (“no credit”):
· Cursory grasp of making activity and inquiry central to elementary science.
· Awkward, unproductive questions when leading an activity that go unrecognized and unaddressed.
· Course readings misrepresented or glossed over rather than well integrated with assignments.
· Overt misconceptions of science content without effort to improve understanding.
· Unexcused absence from class (or incomplete make-up assignment).
“Sky Shadows”
Health and Safety
1. Splash-safe goggles should be worn when any substance being used presents a hazard to the eyes or when there is any potential for glass breakage.
2. Do not taste any science classroom substances and do not drink from or eat off of labware.
3. Do not look directly at the sun. Be careful of reflections of the sun, too.
4. Bulbs for projecting light can become very hot; keep them from touching anything.
5. Do not look directly at the light source.
6. Keep water away from electrical chords and bulbs.
7. Be careful not to trip over an extension cord.
8. Plexiglas may have sharp edges.
9. Don’t scratch the silverware!
Shadows and Sunshine
A. What is a shadow? Can a shadow be seen within a shadow? Do clear objects cast any shadow? Do shadows have color?
B. Take a 2 quart zip lock bag and see what kinds of “shadows” it makes. Try it empty, then with water, and finally with colored water. Can you cast a shadow over a shadow?
C. What kinds of shadows do the rigid, Plexiglas objects cast?
D. What is the shape of the shadow of a ball? Can you make it some shape other than a circle? What different shadow shapes can you make with just one solid object?
E. Take a small tank, go to a relatively dark corner, and shine a flashlight through the water. Look at the beam and the bulb from many angles. Add a few drops of milk to cloud the water. Look again at the flashlight. Do you see any color changes?
F. Nest some jars of water and add different drops of food coloring (red to one, green to another, for example) to the water within each. Examine them from different angles in the sunlight. What colors to different combinations make?
G. Using a small tank or bowl and a piece of Plexiglas (or other flat mirror), submerge the Plexiglas mirror at an angle and intercept sunlight. Sunlight should pass through the water, strike the mirror, and then reflect back out of the water. This design mimics a prism and you should be able to separate sunlight into a spectrum of colors (red, orange, yellow, green, blue, indigo, violet). In effect, you have made model of a raindrop.
Gnomons and Equatorial Sundials
1. Where is the sun at noon? (What do you think about the answer, “directly overhead”?)
2. Are noon and midday the same time?
3. What direction does the shadow of a stick point at midday? (use toothpick, clay, and file folder.)
4. When is the shadow of the stick the shortest?
5. What direction does the shadow point at sunrise? At sunset?
6. If you connect the tips of stick shadows for the entire day, what would be the shape of the line? If you did so on the solstices and equinoxes, what would be the shape of these lines? (Make a sketch.)
7. Consider a globe and the challenge to position it in the natural sunlight oriented the same as the earth at this time and date. In shortest form, what are the directions to follow? When oriented, the sun will illuminate the globe the same as it illuminates the earth- day and night on the globe will correspond to day and night on the earth, for example. (In a small group, agree to a precise, written set of directions for accomplishing this task.)
8. Where is the North Star (Polaris) during daytime?
9. What is the relationship between an observer’s northern hemisphere latitude and the angle above the north horizon of Polaris?
10. Imagine the projection of the earth’s equator onto the “celestial sphere” (the apparent sky dome over our heads). For someone on the equator this line would run from the east point on the horizon, directly overhead (through the zenith point), and down to the west point on the horizon.
11. Where would the projection of the earth’s equator appear to be in the sky for an observer at the North Pole?
12. What is the relationship between an observer’s northern hemisphere latitude and the position of the celestial equator?
13. Given a cylinder, protractor, dowel, pencil, and cutting tool, construct an equatorial sundial (see illustration). Why are telescopes often mounted in this same alignment?
Sky Domes (vegetable strainers; activity from ESS Daytime Astronomy).
Teachers place a wire mesh vegetable strainer over a square of cardboard representing an observer’s horizon. They next mark the points of the compass on the cardboard as well as a point in the center of a circle made by drawing a trace of the strainer’s circumference. A small plastic toy can be used as a prop to demonstrate that an observer stands at this center point, looking outwards at a sky that appears to be a half-spherical dome. The toy must be removed, however, so that shadows can be observed to fall directly upon the point marked as the center of the circle.
By placing pins in the wire mesh, they indicate the location with respect to compass direction and angle above the horizon of various celestial objects (especially the sun) of coordinate system locations (celestial equator, north celestial pole, for example). First, a yellow or gold pin is inserted to represent the sun in the sky at the present moment. Place this pin so that its shadow falls directly upon the center point of the circle on the cardboard. The line of sight for the imaginary observer under the sky dome is now the same as the line of sight to the sun for a person standing at this location on the earth. The task is now to extrapolate the trace of the sun’s motion across the sky for this date.
There are several ways to proceed. By placing pins in the mesh hourly through the day such that the shadow of each one falls on the circle center at the moment of its placement, a series of points will become apparent. These points connect in “dot-to-dot” fashion to make the trace of the sun’s apparent motion for that day. Remove the pins, and replace them by weaving a piece of yarn or thread along this path. The arc thus traced has no bends. The question may arise, “What is the fewest number of points needed to infer the trace of the sun across the sky as modeled on the dome?”
The most common answer is two, although, using some geometric and symmetry principles, even one will do. The reasoning behind this answer depends upon grasp of the orientation of the rotation of the earth with respect to the sky. In this model, as with the true earth, the axis of rotation (our spin) points in the direction of the North Star (Polaris)—or, more precisely, towards as imaginary point in the sky named the North Celestial Pole. This star is found directly above the horizon when looking exactly north. The angle from the horizon to the North Star depends upon the latitude of the observer.
Standing at the North Pole, the North Star is directly overhead. The angle from the horizon is 90 degrees. Standing at the equator, the North Star is found by looking directly north on the horizon. The angle is therefore 0 degrees (the same as the value of the latitude of the equator). Moving 10 degrees northward in latitude from the equator makes the North Star appear to rise 10 degrees above the north point on the horizon. By the time you arrive in Portland, the North Star is found by looking 4 degrees above your horizon’s north point. In other words, the North Star’s angle with respect to the horizon when looking directly north is the same as your latitude. Use your body to point towards the north star on an imaginary walk from the equator to the pole in order to convince yourself that this geometry holds true.
As the earth rotates to the east, objects appear to move from the east to the west across the sky. Dows our spin make objects appear to move closer to or farther from the North Star? No. Thus, stars appear to move across the sky in circles centered upon the North Star when captured by time-lapse photography. On the scale of a single day, all objects in the sky appear to trace paths from east to west in concentric circles whose centers fall on the axis of the earth’s rotation.
Now let us return to the task of inferring the path of the sun: it makes a circle, intercepted by our horizon at sunrise and sunset. (As the earth rotates, our horizon swivels to bring different portions of the sky into view.) The center of this circle falls upon the axis of the earth’s rotation. On the sky dome, this axis is represented by an imaginary line through the center point of the circle (the observer’s location) through the point on the wire mesh representing the location of the North Star—for our latitude, simply midway between the north point on the cardboard and the top most point of the dome. (This description located the same point on the dome seen by the imaginary observer along a line of site 45 degrees above the horizon when looking north.)
Where on the sky dome does a line run standing for the points observed as directly overhead for observers along the earth’s equator? Where in your sky is this line (called the “celestial equator”) found? In both cases, at 90 degrees from the North Star (or, more precisely, the north celestial pole—the place our axis of rotation aims).
Caution: the previous background knowledge is not intended to serve as instructional objectives directly. Instead, inquiry by students ought to occur over the course in the sky. Pay particular attention to paths recorded near the calendar dates when the seasons change. Keep track of the direction on the horizon to sunset and sunrise. If students draw two or three traces of the sun’s path from several observations collected on multiple dates separated by several weeks, they cannot escape observing that these arcs appear nearly parallel-and thus infer shortcuts to drawing arcs from one or two points. In fact, continuous 24 hour recording of the sun’s movement would yield a tightly wound spiral that reaches 23.5 degrees north from the celestial equator on the first day of summer then “descends” to 23.5 degrees south of this line on the first day of winter for residents of the northern hemisphere. On the first days of spring and fall, the sun trace’s a path aligned with the celestial equator. The crossing point on the sun’s northward journey has a special name- the vernal equinox. At the moment the sun appears to arrive at this point due to our spinning and orbiting motions, we say spring begins.
The challenge for teaching is to help students interpret their records of the sun’s apparent motion across the sky dome in terms of an orbital model of the earth in space, where the observer position constantly changes in reference to the relatively fixed position of the sun among the stars (though the sun and the starts are moving rapidly with respect to each other as well—but on the scale of human lifetimes, even civilizations, the constellations appear not to change their configurations).
Pinky Ball & Lunar Phases (CAUTION: DO NOT LOOK DIRECTLY AT THE SUN!)
1. Take a pinky ball and position it as best you can in natural sunlight so that you see a full circle of illumination. Presume your head represents the earth. What are the relative positions of the Sun and the Pinky ball?
2. What angle, with the earth at the vertex, do they form?
3. Move the pinky ball so that the portion illuminated decreases in size from a full circle to a quarter circle. Did you move the ball eastward or westward among the starts to do so?
4. How does the Moon move from night to night with respect to the stars eastward or westward?
5. Keep moving the Pinky ball but be careful not to look directly at the sun. What angle to the earth, ball, and sun form when you see a crescent?
6. Using the pinky ball, model the moon’s orbital motion with respect to the earth through a complete cycle. When is it waning? Waxing?
7. With respect to the earth, what is the shape of the lunar orbit (period of about one month)?
8. With respect to the sun, what is the shape of the earth’s orbit (period of about one year)?
9. With respect to the sun, sketch, a trace of the motion of the moon during the course of a year and compare your sketch with those of others.
10. If drawn to proper scale, what path would this way of thinking about lunar motion trace?
11. Given a table with the diameters of the earth and moon as well as their average distance apart, construct an earth-moon model on a stick that will fit in a closet easily. Use this model to sight from the earth and view the moon changing phases.
12. What is the phase of the moon today?
Circumpolar Umbrella Planetarium
1. Guided by a star chart, stick dots on the inside of an umbrella in order to produce two or more circumpolar constellations.
2. Model the 24-hour motion of these constellations for an observer in Oregon.
3. Model the 24-hour motion of these constellations for an observer at the equator and one at the north pole.
4. For any northern latitude, how would you angle your umbrella planetarium in order to show the apparent stellar motion?
5. The annual motion of the earth in orbit about the sun superimposes another apparent motion on the nightly movement of stars. What is the effect of this orbital motion- in other words, from night to night at exactly the same time where will you find a star of interest? (Or, equivalently, from night to night if observing a star of interest at exactly the same position in the sky, what will be the change in time?)
Analemma
1. An analemma is the trace of the sun’s position for a local observer who records the position of the sun daily at exactly the same time (or at exactly 24 hour intervals). The analemma captures the daily drift of the sun higher (more northerly) and lower (more southerly) as well as its variation in returning to the same location (midday, for example) caused in part by the earth’s orbital speed increasing and decreasing (a result of the shape of our orbit—a bit elliptical, not perfectly circular). The analemma is a graphical depiction of the equation of time, the factor that corrects for the disparity between the mean solar time (known as the 24 hour day) and apparent solar time (what a sundial indicates). Ambitious sundial makers may wish to calibrate their equatorial sundials in order to adjust for the disparity between apparent solar time and mean solar time. You can find such a sundial at the Skamania Lodge in the Columbia Gorge. The true sun does not, or course, appear to move across the sky along the celestial equator at a uniform speed. Due to the eccentricity of the earth’s orbit and the inclination of the plane of the ecliptic with respect to the earth’s rotational axis, the apparent sun is sometimes too early, and sometimes too late-at least in reference to keeping time according to the mean sun.
2. To make an analemma: at exactly 24-hour intervals (or whichever dates the sun casts a shadow at exactly the time you have chosen to observe) mark the tip of your gnomon’s shadow. You must keep the gnomon in exactly the same position. Connect these marks and you should have a distorted figure eight.
“Looking Crazy”
Health and Safety
1. Splash-safe goggles should be worn when any substance being used presents a hazard to the eyes or when there is any potential for glass breakage.
2. Do not taste any science classroom substances and do not drink from or eat off of labware.
3. Do not look directly at the sun. Be careful of reflections of the sun, too.
4. Bulbs for projecting light can become very hot; keep them from touching anything.
5. Do not look directly at the light source.
6. Keep water away from electrical chords and bulbs.
7. Be careful not to trip over an extension cord.
8. Plexiglas may have sharp edges.
9. Don’t scratch the silverware!
The Alice problem: “Do I see myself on, in, or behind the mirror?”
A. Position a flat mirror on a large piece of blank paper. Place a plastic person on the paper, and then position yourself so that you can see the person. Mark on the paper your eye position and the location of the plastic person. Draw a line-of-sight from where you looked from to the mirror. Draw another line from this point at the mirror to the location of the plastic person. Label the ends of these lines “1.” Move the little plastic person and repeat a few times. Label the lines in succession by placing numerals at the eye and object positions. You have thus drawn several angles. Measure them in ways of your own choosing. What, if any, regularities emerge? Try to make a general statement about seeing things and the angles you looked from to see them.
B. On a clean section of the paper and keeping your eye in one position, move the plastic person to various positions and mark them with an “O” if you can still see the figure or with an “X” if you cannot. Move your line-of-sight so that you change its angle to the mirror. Map the “X’s” and “O’s” again. Map the zones where the figure can hide and not hide from you with your gaze coming from just one position.
C. Use two flat mirrors to see a plastic person. Try to draw the line-of-sight from your eye to the figure while keeping to the general angle pattern you determined in part A.
D. Take the SLR camera and focus on an image of yourself in a mirror approximately 10 feet away. Read from the lens ring the distance to the image measured by the camera. Is it 10 feet? More? Less? Determine the relationship between how far from the mirror you stand and what distance to your image the camera measures.
E. Go back to step A and use a ruler to measure distances through the looking glass (its reflection will do). Is the object on, in, at, behind, in front, or through the mirror? Is there truly an image where the figure appears to be? (In other words, does light actually come from where it appears to come from?)
F. Use two strips of Plexiglas. Hinge them with a bit of cloth tape. Place a plastic person in front of them with the strips in a straight line (angle of 180 degrees). Now look at the mirrors as you rotate them inward. Determine a relationship between the angle between the two surfaces and the number of images seen.
G. Add a third strip, use cloth tape, and assemble a kaleidoscope! Enjoy.
H. Class discussion exercise: geometric solutions to image, eye, and object positions.
Shiny things and un-flat mirrors. “Where’s the image now?”
A. Position two flat mirrors at 90 degrees to each other and hold them in front of you. Two shiny spatulas will work fine (plus they have handy handles). If you manipulate them, you can superimpose your reflection until you see a “normal” face (one nose, for example). Look at yourself and wink your right eye. Which eye winks back? How did this happen? Use a sketch to explain to someone else.
B. Gently bend and twist a spatula while gazing at your image reflected on it. Do not attempt to bend plastic, glass, or Plexiglas flat mirrors! What happens to your face? Does it hurt? Rotate the spatula. Does your image move with the rotating surface? Why or why not? Flip the spatula over from one side to the other. Does your image remain the same? Hold the spatula upside down. Does your image turn upside down, too? Are left and right reversed?
C. Look at yourself using other shiny objects: bowls, spoons, cosmetic mirrors. Repeat the rotation and flipping manipulations of these surfaces. Does your image change? Use these utensil mirrors to look at plastic people. Do their images on curved surfaces behave the same as yours? When are they smaller? When are they larger? When do they appear closer, farther, than they actually are? Are the images on, in, behind, or in front of the spoons and bowls?
D. Take a large, shiny serving spoon. Use it to look at a reflection of your finger or the point of a pencil at some distance. Now, very slowly move your finger or pencil closer to the concave (food-holding) side of the spoon. What happens to the image? When is it real and when is it virtual? Repeat, moving the pencil point toward the spoon until it almost touches the surface. Move it out a ways until you have solved the problem of where to position a light bulb in a flashlight.
E. Class discussion exercise: reflection from the tangent to the curve, drawing ray diagrams for converging and diverging mirror surfaces, and the focal point effect.
The broken pencil: “What bends?”
A. Add water to a clear plastic cup, either the short or tall variety (short works best at first, but you may wish to repeat your explorations with both shapes). Immerse a pencil in your cup of water, holding it vertically and in the center. Sketch it carefully. How does its appearance differ, top to bottom? Does the pencil actually bend? What bends?
B. Examine the appearance of the pencil as you lift and lower it, move it side to side, move it front to back, move it around in a circle within the glass, and, either at the same time or as a separate trial, tilt it and straighten it. Look from the side, the top, and the bottom. Do viewers from other orientations see the pencil the same as you?
C. Look down upon the surface of the cup of water with the pencil tilted, submerged, and touching the bottom. It appears bent. Does it look shorter or longer as well? Make a sketch of this configuration. Draw the bent pencil, then draw with dotted lines what the pencil would look like if the glass held no water. Light illuminates the pencil, then propagates from its surface in many, many directions—including to your eyes. However, your eyes see the submerged pencil in a puzzling position. Why? Use the ray diagram to help solve this puzzle. Note that the ray diagram shows two of the many rays of light coming from the tip of the straw in the picture. The solid lines show the actual path of the light from the straw tip. Your eye cannot see the light bend. The dotted lines in the ray diagram are straight-line extensions of the rays that reach your eyes. These dotted lines converge—thus appear to come from a point where the straw is not.
D. Try placing your pencil so that its appearance puzzles you. Work backwards using the idea that straight lines converge to where you apparently see a point on the pencil. Light emanating from the real pencil must bend in order to end up in this trajectory. Make a reasonable guess as to its path through the cup of water. Sketch the path either in vertical or horizontal view.
E. Pause to read Emile and the broken stick. Why and when does light bend?
ESS Optics: Challenges!
Return indoors to work with the “light boxes.” Refer to the ESS Optics Teacher’s Guide excerpt after trying the challenges enumerated below.
A. Cast a beam of light and reflect it with a mirror. Use a stick to make a shadow. Does the shadow reflect? Does the reflection of the shadow resemble the pattern among angles you determined when looking at plastic people with a flat mirror?
B. Using one beam of light and one shadow stick, position the stick so that the shadow doubles (two shadows, one stick and “one” beam). Please explain this anomaly.
C. Cast a beam onto a mirror. Position several others and create zig-zag patterns over a white surface. Use either the wide or narrow slits. What is the regularity or rule you notice about reflecting angles?
D. Fill half-way a few clear plastic jars with water. Check to make certain there are no leaks. Ones with lids are the safest, but you can use the clear cylinders and even plastic tumblers if you are very careful not to spill the water. Place these within beams of light. Make the beams cross. Examine these pathways through the jars. Where does the light bend? In what direction?
E. Position a comb at where beams cross. Examine the fringes of beams that have been altered by your lens-jars. Look for color spectra with and without combs.
F. Now try using the colored filters to mask the projection windows of the light boxes. By using mirrors, combine red, green, and blue to make white light.
G. Overlap the colors. What new colors are formed?
H. Use sticks again to cast shadows. Enjoy the show!
Useful supplies and materials:
| SLR camera Clear plastic cups Small, clear plastic cylinders Pencils Plexiglas strips ESS Optics mirrors and supports Shiny spoons and spatulas Cosmetic mirrors Flashlights Water tanks Milk Food coloring Zip lock bags Milk |
ESS Optics Kit (color projection) Plastic people Newsprint Rulers Protractors Blank, white paper Tennis balls 2-quart ziplock bags Clear plastic geometric shapes Wooden geometric shapes Popsicle sticks Hand lenses |
“Meet the Pillbugs”
Isopod Inquiry
Aim: To translate interest and exploration into carefully designed investigations, then engage in debate over the results.
From the National Science Education Standards:
“Organisms have basic needs . . . [and] can survive only in environments in which their needs can be met. . . . The behavior of individual organisms is influenced by internal cues (such as hunger) and by external cues (such as a change in environment).” (National Science Education Standards [NSES], Life Science Content Standard C for grades K-4, part 1, “the characteristics of organisms,” p. 129.)
“Behavior is one kind of response an organism can make to an internal or environmental stimulus. A behavioral response requires coordination and communication at many levels . . . ” (National Science Education Standards [NSES], Life Science Content Standard C for grades 5-8, part 3, “regulation and behavior,” p. 157.)
“Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organisms’ own species and others, a s well as environmental changes; these responses either can be innate or learned.” (National Science Education Standards [NSES], Life Science Content Standard C for grades 9-12, part 6, “the behavior of organisms,” p. 187.)
Exploration Phase (“Interest and shared experience are basic.”)
Focus Question: What different anatomical features can you find on a pillbug or sowbug (two species of isopods)? (Magnify, sketch, and label “creatively”.) Consult the following outline for more detailed instructions if you wish.
A. Examine isopods with a hand lens or under a microscope to answer:
1. How do isopods appear?
2. In what ways do they differ from each other?
3. How do isopods move?
4. Are there male and female isopods? (Inference based on the observation of ______.)
5. How do isopods grow and develop? (Inference based on the observation of ______.)
B. Construct a “Parts Chart” for a single isopod, labeling the columns as follows:
1. A name for the part.
2. Location of the part.
3. Is it paired with a mirror image part (yes or no)?
4. Color or markings on the part.
5. Shape of the part.
6. Other descriptive comments about the part.
7. Observed use of the part.
8. Inferred use of the part.
C. Using a spoonful of water (no more!) quickly immerse an isopod, then place it on a dry surface to watch its behavior.
1. How does the isopod behave?
2. What might you infer about how isopods breathe?
D. Place a number of isopods and some woody debris in a container and watch them roam around.
1. To what features of their environment do they appear to respond?
2. What can isopods sense?
3. What physical conditions do isopods prefer?
4. What do isopods eat?
Investigation Phase (“Scientists don’t do labs, they design investigations.”)
Focus Question I: In terms of moisture and light, what conditions do pillbugs or sowbugs prefer? (Design the experiment: define independent and dependent variables operationally, collect data, design a test of interaction in part B and graph the data.)
A. Obtain a petri dish, a mist-sprayer, coffee filter, and some black construction paper, or other simple, easily obtained materials (ziplock bag and ice, for example). Design an “isopod preference” experiment that varies one physical factor and records its effect on the behavioral response of about 20 isopods. Before you run a test, commit to a prediction in writing.
B. Using the same petri dish, complicate the experimental design by crossing two physical factors that may interact (for example, moisture and light). Consult Thinking Science by Philip Adey, et al., pp. 119 to 123 for detailed instructions on this approach to experimental design (interaction effects). In graphing your results, place one factor on the x axis and number of pillbugs on the y axis. Plot two lines, one for each level of the second factor.
C. What habitats in the natural world do you think isopods prefer?
Focus Question II: Are isopods social organisms? (Define the variable social operationally; collect data, interpret the evidence, frame an argument.)
A. Many isopods are often found living together in close quarters. Why?
1. Do isopods communicate?
2. Are isopods social organisms?
3. How do isopods avoid predators?
4. Can different kinds of isopods tell each other apart?
5. Do isopods cooperate?
6. Where are isopods found?
7. How does their abundance change through the seasons?
B. Try to figure our whether isopods are social organisms. Be prepared to present our argument, including how you decided to define “social.”
Symposium Phase (“The science is in the debate.”)
A. Talk science following the report form found in Science: A View from the Zoo:
1. Prior studies of isopods and background knowledge relevant to our question.
2. A description of the problem we hoped to solve phrased as a interesting question.
3. The potential importance of solving this problem—the reason we are trying to answer our question.
4. Expression of our question as a testable and fair hypothesis: our prediction of the response of the dependent variable to what we manipulated. (In this section, also describe the conditions you tried to keep unchanged during the course of your experiment.)
5. How we made our measurements and how, in our design, we defined the outcome of interest (our dependent variable).
6. The data we collected represented in table or graph form in order to find any patterns.
7. Our interpretations of these patterns in the data.
8. The answer to our question and the basis of our claim to have solved the problem.
9. The limitations to our claim or the generality of our answer.
10. Further investigations to undertake in light of our study and the reason we feel such additional work might be of importance.
B. Talk science: keep notes as others share; prepare to ask questions about:
1. The design of the investigation, especially the definition of variables.
2. The representation of the data.
3. The interpretation of the results.
4. The implications of the conclusions.
5. The relevance of other studies (for example, your own experiment) to the claims of the investigators.
C. Talk science: contribute to the summing up process:
1. What is the state of our knowledge about terrestrial isopods?
2. What does this knowledge contribute to the bigger picture of how organisms fit their environment?
3. What new questions interest us?
4. How do you feel about these creatures now?
“Messy Solutions”
Health and Safety
1. Splash-safe goggles should be worn when any substance being used presents a hazard to the eyes or when there is any potential for glass breakage.
2. Do not taste any science classroom substances and do not drink from or eat off of labware.
3. Do not use chlorine bleach.
4. Use only very dilute ammonia, if at all.
5. Remember that many common, household products are dangerously toxic and/or corrosive.
6. Bulbs for projecting light can become very hot; keep them from touching anything.
7. Do not look directly at the light source.
8. Keep water away from electrical chords and bulbs.
9. Be careful not to trip over an extension cord.
10. Do NOT add hot water to cups or containers not designed for hot liquids.
Drops
A.
B. (First, learn how to make droppers from straws.) Place drops of water on a waxy surface. Examine them from above and from the side. Use a magnifying glass. Sketch the side-view profile and pay close attention to the zone where the drop touches the waxy surface.
C. Tease, poke, and drag drops with a toothpick. Move one very close to another. What happens when they touch?
D. Sprinkle a pinch of corn starch on your drop. Repeat the sketching of a side-view profile, the teasing, poking, dragging, touching. Tilt your surface. Does the drop slide or roll?
D. Sprinkle a pinch of salt on your drop and examine it with a hand lens. Then sprinkle a tiny pinch of powdered detergent. Try the poking, dragging, and touching again.
E. Repeat any of the above explorations on a new surface—aluminum foil, for example—or with a different liquid—rubbing alcohol, for example.
F. Conduct a “drop race.” Place drops of different solutions in a row on the racing surface. Predict a winner; then tilt the surface and watch to see which drop “runs” the fastest. Note any difference in the tracks each leaves.
G. Why do streams of water break apart into droplets? Why doesn’t rain fall in continuous columns of water?
Salty Teabags
A. Refill a teabag with salt in place of the tea. Fill a clear plastic cup with cool or room temperature water. Immerse the tea bag, but keep it hanging above the bottom of the cup as far as you can. Watch very, very closely for “shimmering”—a hand lens will help.
B. Repeat the teabag refilling procedure. However, this time soak the salty teabag with food coloring before placing it in the clear cup of water. Watch closely as before.
C. Vary the temperature of the water—remembering not to pour hot water into the plastic cups (they WILL melt, so mix some kettle water with tap water to get warm water)—and enjoy watching the shimmerings again. Do any distinct layers form after a while?
Rainbow Straws
A. Fill a set of tall, clear, plastic cups, making each ¾ or more full of just one liquid, by pouring from the five bottles of colored liquids. Place a plastic tub near you as a disposal sink. Take a clear plastic straw and, with the top-end open, submerge it a couple of centimeters into one of the cups of colored water. While it is submerged, place a finger over the top to seal it airtight. Remove the straw. If you are successful and do not squeeze it, the straw will continue to hold its contents of colored liquid. Hold the straw over the plastic tub and release your finger. Why does the liquid not run out of the straw until you remove your finger?
B. Find a way to “double dip” and in doing so create two distinct layers of color that remain unmixed. Does one color appear on the top and the other on the bottom in the same order whenever you succeed or can you reverse the order?
C. The rainbow challenge: How many distinct layers of different color can you stack in your straw by the dipping procedure?
D. Once you have met the challenge as best you can, set up a straw with several layers of colored liquid, keep you finger over the end of the straw, and slowly—very slowly—start to rotate it into an inverted position. What happens to the layers?
Sinking Drops
A. Mess about—being careful not to stain clothing—with drops of food coloring in cups of water. Please be conservative in you use of food coloring.
B. Mix up some “stock solutions” (just a cup) of water of different salinity and color-code them by stirring in food coloring. Mix other solutions of varying salinity and leave them clear. Using a dropper, investigate sinking drops more carefully this time, using either “full strength” food coloring or the “variable salinity” solutions.
C. Try experimenting with white vinegar instead of salt water. You can dilute the vinegar, of course.
D. How can you make “doughnut-shaped” rings? As these rings sink, how do they change? Are they spinning or just sinking and spreading?
E. Take a plastic spoon and stir a cup of plain water vigorously. Stop stirring, right away remove the spoon, and immediately drip in a drop of food coloring. Try doing so in the center of the vortex. Start over and drop the drip in the outer portion of the vortex. Did you see a “curtain” form, as well as rise and sink?
F. The next trial risks spilling, so be careful. It works best if you use a wide, not-to-deep clear plastic tumbler, but the tall ones will do if you spin slowly and very carefully. Place a cup of water in the center of a spice tray. Let it stand so that there is little or no movement in the cup. Add a drop of food coloring near the center of the cup of water so as to produce some sinking doughnuts. As they sink, gently rotate the tray. Let it spin for several rotations while you watch the food coloring disperse. What moves? What doesn’t move?
G. Stop the rotation of the spice tray (not too suddenly!) and watch the mixing in the cup of water with dispersing food coloring.
H. Now that you know the possibilities of the system and its components, investigate your own creations.
Sandra’s Updrops
A. At this point the solutions become very messy. First, set up a water and oil system (layer of vegetable oil above a layer of water) in a clear, plastic cup.
B. Sprinkle a pinch of salt on the oil and observe. Next “dump” about 1/8 teaspoon of salt onto the oil and observe some more. Does the salt dissolve in the oil? Does the salt sink through the oil? Does the salt dissolve in the water? Have you caused any “up-dripping”?
C. Fascinating things may happen at the boundary between oil and water. Try dripping a few drops of food coloring into the oil. Does the food coloring disperse? Sink?
D. Black, India-type ink can be very dense and include a liquid that evaporates very quickly (ink dries faster than water, of course). Try dripping a drop or two of ink into your oil and water system and watch what happens. Remember to look from different angles.
E. You might wish to try stirring some baking soda into the water before adding the layer of oil. Then, instead of food coloring, add drops of vinegar or lemon juice or 7-up. There should be some alcohol left . . .
F. At this point, you have the imagination and curiosity to vary the system in complex ways and create truly fascinating messes—I mean experiments.
Cabbage Juice
Source: http://www.madsci.org/experiments/archive/859332497.Ch.html
See also: http://www2.ncsu.edu/ncsu/pams/science_house/learn/CountertopChem/exp22.html
Make your own acid/base indicator by boiling red cabbage. Use the juice to pH different fluids.
1. 1/2 head of *red* cabbage or so.
2. Metal grater.
3. Pot filled with enough water to cover the grated cabbage.
4. Strainer
5. Some acid/base solutions: for an acid try vinegar, for a base - mix some detergent in water.
Be careful with the fingers when grating the cabbage!
Use only very, very dilute Ammonia in a well-ventilated space.
Do not use household bleach.
1. Grate the cabbage into small pieces and place them in the pot + water.
2. Boil the mixture for 20-30 minutes, until the liquid turns a dark purplish color.
3. Decant the fluid into a glass or jar, pouring through a strainer to remove the cabbage. (Save the cabbage and mix with a little vinegar and you can eat it on hot dogs, etc.) The collected fluid should be bluish/dark purple in color and can be diluted (1/4 juice, 3/4 water).
4. Make up some 'test' acid/base solutions. A good acid to use would be white vinegar. You could also try soda water/sprite or diluted juice from a lemon or orange. You can make a basic solution by mixing some washing detergent in water, or by adding some baking soda (sodium bicarbonate) to water. It's useful to have a control solution of (neutral) water - distilled water is best if you have access to it. DO NOT USE BLEACH.
5. Add a few drops of the cabbage juice to your solutions, and note any color changes. The juice should turn pink in acidic solutions, and green in basic solutions.
6. You can use the indicator on any other solutions of interest, or try drying it on coffee filters to create a simple form of "pH paper."
Red cabbage contains pigments call anthocyanins. The pigments give it the red/purplish color. Anthocyanins belong to group of chemical compounds called flavonoids. For most pH indicators, the compound acquires a proton at low pH (lots of H+) but looses it at higher pH. This seemingly minor alteration is sufficient to alter the wavelengths of light reflected by the compound, thus creating the color change with respect to pH. Anthocyanins behave somewhat inversely in that the pigments "gain" an -OH at basic pH, but loose it at acidic pH.
An acidic solution contains an excess of protons or H+. pH is a measure of how 'acidic' a solution is. The lower the pH, the more acidic the solution. In chemical terms, pH means "the negative log of the concentration of protons" in solution. Chemistry students should recognize this as pH = -log[H+]. If the concentration of H+ is .01M, the pH will be: -log[.01] = -log[10^-2] = -(-2) = 2 (very acidic!).
"Neutral" solutions (water, e.g.) have a pH of 7. This number coincides with the amount of H+ naturally formed in water from the equilibrium reaction: H2O <--> H+ + OH- (H+ experimentally known to be ~10^-7M; OH- is also the same concentration). "Basic" solutions have a pH greater than 7 - meaning they have less free H+ than that of neutral water.
Using red cabbage to prepare an acid/base indicator is described in many science resource books and activity guides. Janice VanCleave's Chemistry for Every Kid, published by John Wiley & Sons, Inc., 1989, describes using cabbage juice and turmeric to prepare paper indicator strips.
One of the most in-depth coverages of using cabbage juice to investigate acids and bases is found in Of Cabbages and Chemistry, one of the Great Explorations in Math and Science (GEMS) guides from the Lawrence Hall of Science at the University of California at Berkeley. GEMS is an ongoing curriculum development project with a variety of excellent teacher guides. A descriptive brochure and ordering information is available. Write or call:
GEMS
Lawrence Hall of Science
University of California at Berkeley 94720
(415) 642-7771
http://www.lawrencehallofscience.org/gems/
“Swing Thing”
Adapted from Pendulums: Investigating Physics with Swinging Objects. Elementary Science Study. Webster Div., McGraw-Hill Co., New York, NY: 1976. Original publication date: 1966, Education Development Center, Inc. ISBN 0-07-018585-9. Currently available through Delta Education, Inc., Box M, Nashua, NH 03061-6012, 1985.
I. Initial Investigation
1. Begin with exploration and manipulation without worrying about a specific question. Simply respond to the general challenge, "What can you find out?"
2. Questions to consider that focus attention on "dying down:"
a) Does the pendulum bob return to the point where it was released?
b) What happens when a pendulum has been swinging for a period of time?
c) Does it travel the same distance during each swing?
d) Is the time it takes to make a swing affected by distance?
e) Is the number of swings a pendulum makes in a specific period of time affected by how long the pendulum has been swinging?
3. Comparing pendulums of different length:
a) How do you calculate the length of a pendulum? (e.g., "from the bottom of the horizontal support to the center of the bob)
b) If the bob is a long cylinder or some other shape other than a sphere, how do you calculate its length?
c) How many swings will a 10 cm pendulum make in 30 seconds? Compare with a 20 cm, 30 cm, and 40 cm pendulums. Make a graph of this information: number of swings on the vertical axis, length of pendulum on the horizontal axis (count swings as a complete cycle--away from and back to the release point is one cycle).
d) Using the graph: How many swings would a 15 cm pendulum make in 30 seconds? A 25 cm one? A 35 cm one?
e) Use the graph to design a pendulum that makes a specific number of swings (your age, for example) in a given period of time.
f) Calculate the length of time for a single swing (on average) for different lengths of the pendulum. Make a graph of this "period" (on the vertical axis) versus "length" (on the horizontal axis). Connect dots to make a smooth curve and extend this line. What shape does it make?
4. Comparing bobs of different mass and shape:
a) Choose a number of different size bobs. When adjusted to the same length, how many swings does each make in 30 seconds? Graph your results (number of swings on the vertical axis, weight of bob on the vertical axis). Find any pattern?
b) What effect does shape have on the motion of a pendulum? Does the substance "swung through" have any effect? (i.e., do pendulums swing the same or different under water?)
c) What effect does changing the number of BBs in a plastic vial have on the number of swings in a fixed period of time? (measuring the height of BBs in the vial is easier, by the way, than counting the number exactly)
d) Can you get odd shapes to swing together?
5. Releasing the bob:
a) Is the number of swings a pendulum makes in a specific period of time affected by the way it is released?
b) If you give a bob a small push, will it make more swings in 30 seconds than a bob gently released with no push?
II. Miscellaneous Challenges
1. How else can you make a pendulum bob swing besides straight back and forth? (trace its motion by following the bob with a pencil)
a) Can you make the bob go in a circle?
b) What other shapes can the swing describe?
c) Which pendulum do you think will win a race back to the starting point: a pendulum swinging in a straight line or one swinging in a circle? How about compared to one swinging in an oval pattern?
d) Time a bob swinging a a big circle, then a little circle. Compare and repeat to check for consistent results.
e) Does the oval shape remain in the same position as the pendulum motion decays? (i.e., does the oval tend to rotate or not?)
f) Can you stop a hand-held pendulum from swinging by moving your hand?
g) Can you move your hand without moving the pendulum?
h) Invent games using golf tees for a pendulum to knock down--predict which ones the pendulum will knock over on each swing.
2. Try "Walking Pendulums:"
a) Suppose pendulum "A" makes 10 trips in the time that "B" makes 7. How many will "B" make while "A" makes 20? Construct charts to compare "round-trips" for one pendulum matched to another. (Note the evolution of language: swings, round-trips, and period.)
b) Adjust two pendulums so that they differ in length by an inch or two. Start both swinging the same way. Count the number of trips made by each as they get out of step ("like legs walking"). Watch for them to come "back in step" while continuing to count. From swing together to swinging in opposition and back to swinging together again, how many round trips does the short pendulum make? How many does the long pendulum make? Does this ratio remain the same as the two motions decay? Does this ratio change when the lengths of each pendulum are increased by one inch?
3. Make COUPLED PENDULUMS: Link two separately hung pendulums of equal length with a thin dowel stick (wrap each string once around the dowel). Stop one bob. LIft and release the other. What happens?
a) What happens when the stick is at an angle?
b) What happens when the strings are of unequal length?
c) What effect does coupling a heavy pendulum to a lighter one have?
c) What effect does a coupling made of string have? of tape? of elastic?
d) Hang six pendulums of three different lengths on a string which is suspended like a clothesline. What happens when you start just one swinging? What do you notice about the equal length pendulums?
III. "Exotic" Pendulum Designs for Further Investigation
1. Stick Pendulum: Use of strip of pegboard (approx. 4 x 25 cm) with a row of holes in the middle of the strip. Swing this pendulum from a nail.
a) Does the stick pendulum swing faster or slower than a string pendulum of the same length?
b) Can you get your stick pendulum and string pendulum to swing together?
2. Rubber Band Pendulums: Loop a piece of string around your pendulum support and attach a rubber band.
a) What happens when a weight is attached to the rubber band?
b) Try making the weight oscillate (move) up and down. Is the oscillation affected by a change in weight or the distance pulled before the release?
c) Do all rubber bands work the same way?
3. Pendulum on a String: Stretch a string between two objects. Tie onto this string several pendulums.
a) What happens when one pendulum is put into motion?
b) What happens when two pendulums are put into motion?
c) What happens if the weight of the bobs is changed?
4. Salt Pendulums:
a) Use a cone shaped cup or some other funnel-shaped container for a bob. Fill it with fine sand, salt, or a dry powder. Watch as this material leaves a trace as the pendulum swings and the sand/powder/salt escapes steadily through a hole in the bottom of the bob.
b) What designs can you make?
c) What shapes can be made if the surface the sand falls on moves steadily past the pendulum?