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PHY 241
Your 'collaborative labs' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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7/10 07:40
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You will participate during the semester in two series of collaborative lab activities.
The first is designed to be relatively painless, and to begin to develop a degree of teamwork and collaboration.
These activities are designed for teams of four individuals, each with a specific function:
· The designer will come up with the idea for the activity and will specify for other team members how the activity is to be conducted.
· The experimenter will follow the designer's instructions to set up the experiment and collect data.
· The analyzer will analyze the data.
· The interpreter will describe what the results mean.
For each series of activities, you will participate in four different investigations, one as designer, another as experimenter, another as analyzer and another as interpreter.
As each investigation progresses, you will follow the work of your fellow team members.
Please summarize the above, as best you can, in your own words:
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I will participate as a member of a lab group of four students to complete two activities this semester. Each activity will consist of four investigations. Each member of the lab group will be assigned a different role in each investigation; that of designer, experimenter, analyzer and interpreter.
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The first series of activities will be spread out over the first half of the semester, the second series over the second half of the semester.
The first series will be based on systems you have seen in the Key Systems videos.
You will begin by describing at least three ideas for investigations related to the Key Systems videos. Valid ideas will ultimately be developed proposals, each of which will describe a question that could be investigated and tested using simple materials such as those seen in the videos. You will eventually develop three proposals, one of which will be chosen for an investigation. You will be the designer for that investigation.
At this point we're just beginning to explore ideas for the first series of investigations. Your instructor will work with you to further develop your ideas, and perhaps to explore other related possibilities.
Right now you don't have a wide variety of experimental techniques available to you, so this first series of investigations will be relatively simple.
List below three ideas for things you think might be fairly easy to test, based on the systems you have seen so far.
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Key systems we’ve viewed so far: 1) pendulum, 2) marble rolling down incline, 3) straw rotating on die, 4) chain of rubber bands, 5) fluid draining from cylinder, 6) stack of dominoes, and 7) beads in a box.
Ideas: 1) What is the relationship between the steepness of the incline and the speed of the ball as it leaves the incline? 2) Is there a relationship between the height of the water in the cylinder and the maximum horizontal distance reached by water being discharged? 3) Is there a relationship between the tension on the rubber bands and the frequency of the back-and-forth motion?
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Discuss your first idea. How do you think it might be tested? What sort of items do you think might be required? How do you think your idea might be tested?
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The presence of a relationship between the steepness of the incline and the speed of the ball as it leaves the incline can be investigated by changing the slope of an incline of known length and measuring how long it takes for the ball to reach the end of the incline.
One would need:
· an incline
· a ball
· an instrument for measuring length calibrated in mm (ruler, tape, etc.)
· an instrument for measuring angles calibrated in degrees (optional)
· a timer
One would first measure the length of the incline. Then, one would run a series of trials - measuring the angle of the incline, releasing the ball, and then recording how long it took the ball to roll the length of the incline. One could graph the data with the angle of the incline being the independent variable and the time required to travel the length of the incline as the dependent variable. One could also calculate the speed of the ball as it leaves the incline by doubling the calculated average speed of the ball. The speed of the ball as it exited the incline could also be graphed vs. the angle of the incline. An assumption of constant acceleration is needed in order to simply double the average velocity to get the final speed of the ball, and that can be tested by recording how long it takes the ball to travel several distances down the incline. The acceleration of the ball can be determined using those data. Several measurements should be made at each angle.
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Discuss your second idea. How do you think it might be tested? What sort of items do you think might be required? How do you think your idea might be tested?
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The relationship between the height of the water and the distance discharged can be investigated by allowing water to exit the bottom of a cylinder and measuring the height of the water column and the maximum distance discharged at different water heights.
One would need:
· some fluid (water)
· a cylinder with a uniform diameter
· something to make a circular hole in the side of the cylinder near the bottom
· a stopper (cork, etc.) to close the circular hole until the trial is started
· an instrument for measuring distances calibrated in mm (ruler, tape, etc.)
· a marker (waterproof pen, Sharpie, etc.) if the cylinder does not have heights delineated
· a pan, glass, or something similar to capture the water being discharged
· a stool, box, or some other item that will elevate the cylinder above a base.
One would first drill a hole in the side of the cylinder near the bottom. The hole should be somewhat smaller than the diameter of the cylinder. A cork or other stopper is then placed in the hole. If the cylinder does not have elevations marked on the side - use the ruler and pen to mark ‘standard’ elevations (say, every 2 cm). Then, place the cylinder on the edge of the stool or box with the hole facing ‘out’ so that the discharged fluid does not hit the stool or box - but falls on the base. It may take a few trials, but the height of the stool/box should be such that the fluid has achieved a vertical drop by the time it falls on the base.
Place fluid in the cylinder. Remove the stopper. One person watches the fluid level drop and cries out “Mark!” when the fluid level reaches one of the ‘standard’ heights. Another person marks the location where the fluid strikes the base each time the first person cries “Mark!” Following this trial - the distances that the fluid reaches are measured and correlated with its corresponding ‘standard’ elevation. These data can be graphed with the height of the fluid being the independent variable and the distance discharged being the dependent variable. Trials should be repeated several times.
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Discuss your third idea. How do you think it might be tested? What sort of items do you think might be required? How do you think your idea might be tested?
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The relationship between the tension on the rubber band chain and the frequency of the oscillation can be investigated by measuring the tension on the rubber band chain and measuring the frequency of the oscillation.
One would need:
· several rubber bands
· a tensiometer (a tension scale)
· two eye hooks
· a frame (or something between which the rubber band chain can be stretched)
· a timer
· an instrument for measuring distances (calibrated in mm)
One would fix one of the eye hooks in each side of a frame. Attach one end of the rubber band chain to one of the eye hooks and the other end of the rubber band chain to the tensiometer. Stretch the rubber band chain by pulling on the tensiometer until the end of the rubber band chain is at the other eye hook. Record the tension on the rubber band chain. Remove the tensiometer and attach that end of the rubber band chain to the eye hook.
Extend the rubber band chain at its mid-point a known distance from its centerline and release it. Record the frequency of its oscillation.
Remove one end of the rubber band chain from an eye hook and attach it to the tensiometer. Adjust the frame so that the eye hooks are farther apart. Stretch the rubber band chain by pulling on the tensiometer until the end of the rubber band chain is at the other eye hook. Record the tension on the rubber band chain. Remove the tensiometer and attach that end of the rubber band chain to the eye hook. Record the frequency at the new tension as described above. Repeat several times for each tension - record the frequency at several tensions.
Graph the data using the tension as the independent variable and the frequency of oscillation as the dependent variable.
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Your instructor is trying to gauge the typical time spent by students on these activities. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
· Approximately how long did it take you to complete this activity?
About half an hour, maybe 40 minutes.
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Very good.
We'll be setting these up this weekend.
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