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course Phy 202
What do you expect will happen? Answer the following:Will the water stream tend to travel longer and longer distances before striking the surface below, shorter and
shorter distances, or will the distance tend to increase at times and decrease at times? Why do you think the
distance traveled by the stream will behave as you say?
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The water stream should travel shorter and shorter distances as the water pours out of the bottle.
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Will the speed of the escaping water increase, decrease, or sometimes increase and sometimes decrease? Explain your
thinking.
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The speed of the escaping water will decrease since the height of the water is lowering. There will be less
potential energy.
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Clearly the water level will decrease. Will it decrease more and more quickly, more and more slowly, or sometimes
more quickly and sometimes more slowly? Explain your thinking.
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It will decrease more and more slowly. The potential energy change will decrease less and less rapidly.
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Now set up and prepare to take some measurements:
Punch or cut a hole about 1/8 inch (.3 cm) in diameter in the side of the bottle, at a point where the side of the
bottle is vertical, within a few centimeters of the bottom of the bottle. If you cut the hole, a triangle about 1/8
inch on a side is about right.
Your initial materials will include short open pieces of tubing, one whose diameter is the same as that of the 'cap'
on the bottlecap and tube, the other having the same diameter as the tube. Insert the larger of these pieces into
the hole. The piece should fit fairly tightly in the hole, so when the bottle is filled much more of the water that
flows from the bottle will flow through the tube rather than around it. You can test this by filling the bottle,
placing your thumb over the end of the tube, and seeing how much water leaks out. Then move your thumb and verify
that the water flows out much more rapidly.
Mark three points on the bottle, one at the top of the cylindrical section of the bottle, one halfway between the
first mark and the hole, and one halfway between the second mark and the hole. Measure the three distances,
relative the the hole, with reasonable accuracy.
You will set the bottle it a vertical position and release your thumb. You will time the fall of the water level,
reporting the clock times at which the water reaches the first mark, and each subsequent mark.
You will report the vertical positions of the three lines, relative to the hole, and the observed clock times. Your
data will be used to determine the duration of each of three intervals:
During the first interval the water level falls from the highest mark to the second-highest.
During the second interval the water level falls from the second mark to the third.
During the third interval the water level falls from the third mark to level of the hole. The water will be
considered to have reached the level of the hole when it starts falling from the bottle in separate drops rather
than a stream or a continuous series of drops.
Before you actually perform the experiment make some additional predictions:
Which of the four intervals will last the longest, and which will be the shortest?
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The last interval will be the longest.
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List the predicated intervals in order, from the longest to the shortest, and explain your thinking:
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Third,Second, First
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Did you predict the order of the four intervals correctly?
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No
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Now run your first trial. (You will also run a second trial, in which the short piece of thinner tubing is inserted
into the larger piece to narrow the flow).
Report your data, and explain what it means. If you used the TIMER include a copy of the display of times (you can
just copy and paste the display into a document).
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1 94.35938 94.35938
2 105.0664 10.70703
3 112.8164 7.75
4 125.5625 12.74609
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Determine, as accurately as you can using a clock or watch with a second hand, the clock times at which the water
reaches the first mark, the second, the third and the clock time at which the flow from the hole reduces to the
point where it leaves the hole in distinct drops.
Run your second trial, in which the short piece of thinner tubing is inserted into the larger piece to narrow the
flow.
Report your data, and explain what it means. If you used the TIMER include a copy of the display of times (you can
just copy and paste the display into a document).
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1 618.4336 618.4336
2 633.1484 14.71484
3 642.4688 9.320313
4 649.5078 7.039063
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Determine, as accurately as you can using a clock or watch with a second hand, the clock times at which the water
reaches the first mark, the second, the third and the clock time at which the flow from the hole reduces to the
point where it leaves the hole in distinct drops.
&#Your work on this lab exercise looks good. Let me know if you have any questions. &#