Brief flow experiment

#$&*

course phy122

1/25 1

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?

I expect that the stream will flow quickly from the first to the second line (marker) after that time I expect that the flow will start to decrease and that it will take more elapsed time from the second to the third marker. I think that the distance of the stream will initially be greater and then decrease as the level in the bottle decreases. As the volume in the bottle decreases, the force will decrease behind the stream due to decreases in both kinetic energy and positional energy.

****

#$&*

Will the speed of the escaping water increase, decrease, or sometimes increase and sometimes decrease? Explain your thinking.

****

The speed will increase initially when the tube is released of pressure and will start to decrease as the water level decreases. I’m thinking that the force behind the stream coming out of the bottle will begin to decrease at some point from the first line to the second line. As the water level begins to drop the force will be greater, as the level decreases more so will the force of the stream, finally when it is closer to the bottom line or hole, the force should be minimal.

#$&*

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.

****

Initially, the water level will decrease more and more quickly and then more and more slowly. As the level of water decreases initially it will have greater kinetic and positional energy, thus forcing the water out of the tube at a faster rate. After it has decreased to a certain distance the kinetic energy and positional energy will decrease, thus decreasing the speed of the water level decrease.

#$&*

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 last interval will take the longest.

#$&*

List the predicated intervals in order, from the longest to the shortest, and explain your thinking:

****

Longest: will be from the hole to a drip; I am thinking that it will take longer at this point for the water to leave the bottle due to the greatest decrease in kinetic/positional energy.

Next Longest: from the middle line to the hole; as the water level decreases there will not be as much positional energy pushing the water out of the bottle.

Shortest: from the first line to the middle line; this interval will pass the quickest due to increased positional and kinetic energy.

#$&*

Did you predict the order of the four intervals correctly?

****

No, I did not. I thought that I had prior to performing the experiment. The level between the 2nd line and the third line(hole) took longer than it did for the stream to turn to a drip.

#$&*

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 3207.176 3207.176

2 3215.32 8.144531

3 3232.816 17.49609

4 3239.117 6.300781

The data shows that the time elapsed between the first line to the second line was 8 seconds, between the second and third interval was 17 seconds, and between the third and fourth was 7 seconds.

#$&*

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).

****

Using the second hand on my watch, I timed the seconds for the water to leave the bottle with a smaller piece of tubing inserted into a larger piece of tubing. Starting at the top mark the second hand revealed 18 seconds, at the 2nd mark the second hand revealed 25 seconds, at the third mark the second hand revealed 37 seconds, and at the point where the water went from a stream to a drip the second hand revealed 46 seconds. These times indicate that it took 7 seconds for the water to descend from the top line to the middle line, it took 12 seconds from the middle line to the hole, and 9 seconds for the water to come to a drip.

#$&*

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.

"

Self-critique (if necessary):

------------------------------------------------

Self-critique rating:

Brief flow experiment

#$&*

course phy122

1/25 1

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?

I expect that the stream will flow quickly from the first to the second line (marker) after that time I expect that the flow will start to decrease and that it will take more elapsed time from the second to the third marker. I think that the distance of the stream will initially be greater and then decrease as the level in the bottle decreases. As the volume in the bottle decreases, the force will decrease behind the stream due to decreases in both kinetic energy and positional energy.

****

#$&*

Will the speed of the escaping water increase, decrease, or sometimes increase and sometimes decrease? Explain your thinking.

****

The speed will increase initially when the tube is released of pressure and will start to decrease as the water level decreases. I’m thinking that the force behind the stream coming out of the bottle will begin to decrease at some point from the first line to the second line. As the water level begins to drop the force will be greater, as the level decreases more so will the force of the stream, finally when it is closer to the bottom line or hole, the force should be minimal.

#$&*

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.

****

Initially, the water level will decrease more and more quickly and then more and more slowly. As the level of water decreases initially it will have greater kinetic and positional energy, thus forcing the water out of the tube at a faster rate. After it has decreased to a certain distance the kinetic energy and positional energy will decrease, thus decreasing the speed of the water level decrease.

#$&*

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 last interval will take the longest.

#$&*

List the predicated intervals in order, from the longest to the shortest, and explain your thinking:

****

Longest: will be from the hole to a drip; I am thinking that it will take longer at this point for the water to leave the bottle due to the greatest decrease in kinetic/positional energy.

Next Longest: from the middle line to the hole; as the water level decreases there will not be as much positional energy pushing the water out of the bottle.

Shortest: from the first line to the middle line; this interval will pass the quickest due to increased positional and kinetic energy.

#$&*

Did you predict the order of the four intervals correctly?

****

No, I did not. I thought that I had prior to performing the experiment. The level between the 2nd line and the third line(hole) took longer than it did for the stream to turn to a drip.

#$&*

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 3207.176 3207.176

2 3215.32 8.144531

3 3232.816 17.49609

4 3239.117 6.300781

The data shows that the time elapsed between the first line to the second line was 8 seconds, between the second and third interval was 17 seconds, and between the third and fourth was 7 seconds.

#$&*

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).

****

Using the second hand on my watch, I timed the seconds for the water to leave the bottle with a smaller piece of tubing inserted into a larger piece of tubing. Starting at the top mark the second hand revealed 18 seconds, at the 2nd mark the second hand revealed 25 seconds, at the third mark the second hand revealed 37 seconds, and at the point where the water went from a stream to a drip the second hand revealed 46 seconds. These times indicate that it took 7 seconds for the water to descend from the top line to the middle line, it took 12 seconds from the middle line to the hole, and 9 seconds for the water to come to a drip.

#$&*

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. &#