#$&*
course Phy 122
1/26 10pm
Brief Flow Experiment
Use a plastic soft-drink bottle and the TIMER program, as well as two short open tubes from the Initial Materials package (sent for free when you submitted your address, according to the email request made previously). If you don't yet have those materials you can improvise with a drinking straw and a plastic soft-drink bottle.
The experiment just asks fora few predictions and some data, and once set up takes only a few minutes to run. Don't go to a lot of trouble trying to be overly precise, but do try to be reasonably accurate (e.g., +- a second on timing, +- a few millimeters on positions of the three lines, +- a centimeter or two on the horizontal range of the stream). You'll be refining things and taking a little more care on followup trials. You should easily be able to get this done before Monday.
Do spend some time on the problems and submit what you are able to get prior to Monday's class. You'll learn a lot more in class if you do so. We'll be going over the questions in class.
You are going to do the following (don't do it yet; predict first what will happen):
Punch a hole the side of the bottle, near the bottom.
Insert a piece of tubing into the hole to direct the flow of water from the bottle.
Fill the bottle with water.
Set it on a tabletop or on the counter next to the sink (or on the ledge of a bathtup, etc.--any setup will do as long as the bottle rests on a level surface, and the escaping stream has at least 15 cm to fall before it hits something).
Let the water run out, with the stream falling freely to the surface below.
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?
****
The steam will travel shorter and shorter distances because as the volume of water in the bottle decreases it's weight does as well and this means less pressure on the water leaving the tube.
#$&*
Will the speed of the escaping water increase, decrease, or sometimes increase and sometimes decrease? Explain your thinking.
****
The speed with decrease as well because their is less downward pressure as the volume decreases in the bottle.
#$&*
Clearly the water level will decrease. Will it decrease more and more quickly, more and more slowly, or sometimes more quickly and sometimes more slowly? Explain your thinking.
****
I think the level will decrease more slowly because the water is leaving the bottle less slowly
#$&*
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?
****
The third interval will last the longest. The first interval will be the shortest. I only see three intervals, not four.
#$&*
List the predicated intervals in order, from the longest to the shortest, and explain your thinking:
****
Third, second, first.
The third will be the longest because the pressure is the least. The first and the second may be similar because the pressure is greater during the first, but during the second there the volume of water that needs to exit is half that of the first. This may be close.
#$&*
Did you predict the order of the four intervals correctly?
****
No. the second interval was the fastest
#$&*
Now run your first trial. (You will also run a second trial, in which the short piece of thinner tubing is inserted into the larger piece to narrow the flow).
Report your data, and explain what it means. If you used the TIMER include a copy of the display of times (you can just copy and paste the display into a document).
****
1 206.9453 206.9453
2 222.9063 15.96094
3 234.1563 11.25
4 257.8828 23.72656
Basically, this means that it took 15.961 seconds to go from the first (highest) mark to the second mark. It then took 11.25 seconds to go from the second mark to the third. Finally it took 23.727 seconds to go from the third mark to the hole.
First mark is 130 mm upwards from the hole. Second mark is 65 mm upward from the hole. Third mark is 32.5 mm upwards from the hole.
#$&*
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).
****
1 1155.789 1155.789
2 1186.844 31.05469
3 1210.016 23.17188
4 1254.305 44.28906
Basically, this means that it took 31.055 seconds to go from the first (highest) mark to the second mark. It then took 23.172 seconds to go from the second mark to the third. Finally it took 44.289 seconds to go from the third mark to the hole. Again the third interval interval was the slowest and the middle interval was the fastest.
This run compared to the first trial was slower over all because of the narrower tube. As would be expected, the size of the tube limits the volume of water that can exit the bottle at a given time, thus it takes longer to empty the bottle.
First mark is 130 mm upwards from the hole. Second mark is 65 mm upward from the hole. Third mark is 32.5 mm upwards from the hole.
#$&*
???I didn't get the short pieces of tubing with the initial kit so I used a straw for the first part. To narrow the tube for the second trial, I found a tube that used to run water to a refrigerator. It had the same outside ""girth"" as the straw but a smaller interior girth so I shaved down the outside until it fit inside the straw. If we need the two pieces of tube you mentioned for future labs, can you send me them???"
@&
It was my fault for not including the tubing pieces. I'll send them out tomorrow, in case they are needed before the full lab package is purchased.
In any case good work with the improvisation.
*@
#$&*
course Phy 122
1/26 10pm
Brief Flow Experiment
Use a plastic soft-drink bottle and the TIMER program, as well as two short open tubes from the Initial Materials package (sent for free when you submitted your address, according to the email request made previously). If you don't yet have those materials you can improvise with a drinking straw and a plastic soft-drink bottle.
The experiment just asks fora few predictions and some data, and once set up takes only a few minutes to run. Don't go to a lot of trouble trying to be overly precise, but do try to be reasonably accurate (e.g., +- a second on timing, +- a few millimeters on positions of the three lines, +- a centimeter or two on the horizontal range of the stream). You'll be refining things and taking a little more care on followup trials. You should easily be able to get this done before Monday.
Do spend some time on the problems and submit what you are able to get prior to Monday's class. You'll learn a lot more in class if you do so. We'll be going over the questions in class.
You are going to do the following (don't do it yet; predict first what will happen):
Punch a hole the side of the bottle, near the bottom.
Insert a piece of tubing into the hole to direct the flow of water from the bottle.
Fill the bottle with water.
Set it on a tabletop or on the counter next to the sink (or on the ledge of a bathtup, etc.--any setup will do as long as the bottle rests on a level surface, and the escaping stream has at least 15 cm to fall before it hits something).
Let the water run out, with the stream falling freely to the surface below.
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?
****
The steam will travel shorter and shorter distances because as the volume of water in the bottle decreases it's weight does as well and this means less pressure on the water leaving the tube.
#$&*
Will the speed of the escaping water increase, decrease, or sometimes increase and sometimes decrease? Explain your thinking.
****
The speed with decrease as well because their is less downward pressure as the volume decreases in the bottle.
#$&*
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.
****
I think the level will decrease more slowly because the water is leaving the bottle less slowly
#$&*
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?
****
The third interval will last the longest. The first interval will be the shortest. I only see three intervals, not four.
#$&*
List the predicated intervals in order, from the longest to the shortest, and explain your thinking:
****
Third, second, first.
The third will be the longest because the pressure is the least. The first and the second may be similar because the pressure is greater during the first, but during the second there the volume of water that needs to exit is half that of the first. This may be close.
#$&*
Did you predict the order of the four intervals correctly?
****
No. the second interval was the fastest
#$&*
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).
****
1 206.9453 206.9453
2 222.9063 15.96094
3 234.1563 11.25
4 257.8828 23.72656
Basically, this means that it took 15.961 seconds to go from the first (highest) mark to the second mark. It then took 11.25 seconds to go from the second mark to the third. Finally it took 23.727 seconds to go from the third mark to the hole.
First mark is 130 mm upwards from the hole. Second mark is 65 mm upward from the hole. Third mark is 32.5 mm upwards from the hole.
#$&*
Determine, as accurately as you can using a clock or watch with a second hand, the clock times at which the water reaches the first mark, the second, the third and the clock time at which the flow from the hole reduces to the point where it leaves the hole in distinct drops.
Run your second trial, in which the short piece of thinner tubing is inserted into the larger piece to narrow the flow.
Report your data, and explain what it means. If you used the TIMER include a copy of the display of times (you can just copy and paste the display into a document).
****
1 1155.789 1155.789
2 1186.844 31.05469
3 1210.016 23.17188
4 1254.305 44.28906
Basically, this means that it took 31.055 seconds to go from the first (highest) mark to the second mark. It then took 23.172 seconds to go from the second mark to the third. Finally it took 44.289 seconds to go from the third mark to the hole. Again the third interval interval was the slowest and the middle interval was the fastest.
This run compared to the first trial was slower over all because of the narrower tube. As would be expected, the size of the tube limits the volume of water that can exit the bottle at a given time, thus it takes longer to empty the bottle.
First mark is 130 mm upwards from the hole. Second mark is 65 mm upward from the hole. Third mark is 32.5 mm upwards from the hole.
#$&*
???I didn't get the short pieces of tubing with the initial kit so I used a straw for the first part. To narrow the tube for the second trial, I found a tube that used to run water to a refrigerator. It had the same outside ""girth"" as the straw but a smaller interior girth so I shaved down the outside until it fit inside the straw. If we need the two pieces of tube you mentioned for future labs, can you send me them???"
@&
It was my fault for not including the tubing pieces. I'll send them out tomorrow, in case they are needed before the full lab package is purchased.
In any case good work with the improvisation.
*@