ICE CIRCLE EXERCISE
by Grandpa Cliff March 2011
This is an exercise in logical, step-by-step thinking, the kind often used by scientists. If you are curious about the things around you, this kind of thinking may help you gain a better understanding of the things you see, and how they got that way.
Watch the video below. Answer the questions and think about how each answer affects the ice circle. Click on the number of the answer to see if your answer agrees with mine. Don't peak at them until you have tried to answer all questions. If you get any wrong, it would be helpful to read everything again, and play the video an extra time or two.
One way to restart the video before it has finished is to click your internet browser's refresh or restart button near the top of the screen.
Go to Question: 1 2 3 4 5 6 7 8 9 10 11 12
13 14 15 16 17 18 19 20 21 22 23 24 25 Comment
(1:02) Ice Circle in Canada
For this exercise, think of the top of the video as 12:00 on a clock, and the bottom as 6:00.
1) Which way is the stream water flowing? A1 Video
2) Which way is downstream? A2 Video
3) Does the water flowing along the surface of the stream come in contact with the ice circle? A3 Video
4) Does water flow under the ice? A4 Video
5) Does the main current of the stream flow under the entire ice circle or just part of it? A5 Video
6) If it is only under part of it, which part is it under? A6 Video
7) What is the name of the force the flowing water exerts on the bottom of the ice? A7 Video
8) Is the ice circle rotating? If so, is it rotating clockwise or counterclockwise?
[Rotating means to spin on an axis. An axis is a central point. The center of a bicycle wheel would be where its axis is located.] A8 Video
9) The ice circle is sticking out into the stream current. Does the surface water collide with the ice? Does it push the ice circle downstream? A9 Video
10) Does the water flowing downstream under the ice circle help to push it downstream? A10 Video
11) When the video begins, the gap between the ice circle and the stationary ice at 9:00 is quite wide. During the video, the water gap gets narrower at 7:00, then 8:00, then 9:00 and finally at 10:00. In what direction has the ice circle been moving? A11 Video
12) Has the water been moving in the same direction as the ice? A12 Video
13) Has the water been moving dowstream or upstream? A13 Video
14) What does this tell us about the water flow under the various parts of the ice circle? A14 Video
15) What word describes that pattern of water flow under the ice? A15 Video
16) Does the ice move in a straight line? A16 Video
17) If a pebble was resting at the center of the ice circle, as the ice circle moved around, what geometric figure would describe the path that the pebble takes over and over again if you watched it for an hour? A17 Video
18) When the ice circle rubs against the stationary ice, little ice chips are scraped off. They look like snow from a distance. Would you expect the ice chips to be at the edge of the ice circle? A18 Video
19) Would you expect the ice chips to be at the edge of stationary ice? A19 Video
20) Look carefully. Are the ice chips at the edge of both? [This can best be seen at about time 0:53 in the video. To see this best, pause the video. Then, put your cursor on the thin red line just above the bottom edge of the video. A bar appears. As you move the cursor along the bar, it shows changing times. When you reach 0:52 or 0:53, click on the bar. The paused picture should change to the one I want you to see. If it doesn't work that way for you, play the video until it reaches that time, then pause it.] A20 Video
21) Are the ice chips at the edge of either the ice circle or the stationary ice? A21 Video
22) Why is there a band of stationary ice with a darker color at 9:00? [This can best be seen near the end of the video, especially at the time where you paused the video.] A22 Video
23) Now, why do you think that the ice chips aren't at the edge of the ice circle? A23 Video
24) If a bicycle is resting upside down on the seat and handle bars, what would happen to a wheel if you quickly push the top of one of the tires to the right? A24 Video
25) How is the situation with the bicycle wheel similar to the situation with the ice circle? A25 Video
26) Read the final comment. Comment
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Answers:
Final Comment: Although the outside edge of the ice circle is just about a perfect circle, the rotating ice circle itself does not float around in a perfectly circular path. Therefore, the stationary ice does not have a circular shape where it contacts the ice circle. As it moves around, the path of the ice circle is elliptical, and therefore the ice circle grinds the edge of the stationary ice into the same shape. Since the stationary ice does not surround the ice circle, its edge cannot be in the shape of an entire ellipse. It is just an arc of an ellipse. Video
25) The main current, which has the stronger force, is pushing on only one side of the ice circle (near the outside edge at 12:00). That causes the ice circle to rotate. Q25 Video
23) New ice formed on the outside edge of the ice circle. Q23 Video
22) This is new ice formed after the ice chips on the stationary ice were formed. Q22 Video
17) Circle or ellipse Q17 Video
14) Near the current, it flows downstream, but away from the current it flows upstream (opposite directions). Q14 Video
12) It has been flowing in the opposite direction to the stream current. It has been moving upstream. Q12 Video
6) The part at 12:00. Q6 Video
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Visitors since 9 Mar
2011