#$&*
phy 231
Your 'ball down ramp' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
#$&* Your general comment **
July 4th, 6:22 pm
#$&* Will a steeper ramp give greater or lesser time? **
A ball is timed as it rolls from rest to the end of a ramp. The slope of the ramp is varied. Preliminary conclusions are drawn about the motion and the effect of ramp slope. A subsequent lab exercise uses the data from this lab to reach additional conclusions.
Most students report completion times between 45 minutes and 75 minutes hour, with a few reporting times as short as 25 minutes or as long as 2 hours. Median time of completion is around 1 hour.
Timing Ball down Ramp
The picture below shows a ball near the end of a grooved steel track (this steel track is a piece of 'shelf standard'); the shelf standard is supported by a stack of two dominoes. Your lab materials package contains two pieces of shelf standard; the shelf standard shown in the figure is white, but the one in your kit might be colored black, gold, silver or any of a variety of other colors.
If a ball rolls from an initial state of rest down three ramps with different slopes, the same distance along the ramp each time, do you think the time required to roll the length of the ramp will be greatest or least for the steepest ramp, or will the interval on the steepest ramp be neither the greatest nor the least? Explain why you think you have correctly predicted the behavior of the system.
Your answer (start in the next line):
I predict that the steeper the ramp the least time it will take for the ball to roll down that ramp. You are increasing the slope and therefore the ball will roll faster. The faster it rolls the quicker it gets down the ramp or the “least” time it will take.
#$&*
If we write down the slopes from least to greatest, next to the time intervals observed for those slopes, would you expect the time intervals to be increasing or decreasing, or do you think there would be no clear pattern? Explain why you think you have correctly described the behavior of the numbers in the table.
Your answer (start in the next line):
If the slopes are listed from least to greatest next to their corresponding time intervals, I would expect the time intervals to be decreasing. The reasoning is the same as the last question: the higher the slope the faster the ball will roll down, therefore the time will be the shortest on the greatest slope.
#$&*
Set up the shelf standard ramp on a reasonably level table, using a piece of 30-cm shelf standard and a single domino under the high end of the ramp. Position the dominoes so that the last .5 cm of the ramp extends beyond the point where the ramp contacts the domino,.and do the same in all subsequent setups.
Set the bracket on the table, touching the lower end of the ramp so that a ball rolling down the ramp will strike the bracket..
Mark a point about 3 cm below the top end of the ramp. Place a domino on the ramp to its high end is at this point, and place the ball just above the domino, so the domino is holding it back. Quickly pull the domino away from the ball so the ball begins to roll freely down the ramp. Allow the ball to roll until it strikes the bracket.
The bracket will probably move a little bit. Reset it at the end of the ramp.
Determine how far the ball rolled from release until it struck the bracket.
Now repeat, but this time use the TIMER. The first click will occur at the instant you release the ball, the second at the instant the ball strikes the bracket. Practice until you are as sure as you can be that you are clicking and pulling back the domino at the same instant, and that your second click is simultaneous with the ball striking the bracket.
When you are ready, do 5 trials 'for real' and record your time intervals.
Then reverse the system--without otherwise changing the position of the ramp, place the domino under the left end and position the bracket at the right end.
Time 5 trials with the ramp in this position.
In the space below, give the time interval for each trial, rounded to the nearest .001 second. Give 1 trial on each line, so that you will have a total of 10 lines, the first 5 lines for the first system, then 5 lines for the second system.
Beginning in 11th line give a short narrative description of what your data means and how it was collected.
Also describe what you were thinking, relevant to physics and the experiment, during the process of setting up the system and performing the trials.
Your answer (start in the next line):
1.625
1.703
1.625
1.703
1.58
2.047
2.016
1.984
2.016
2.031
If the conditions were perfect and the clicking of the TIMER at release and hitting the metal bracket were exact the time interval would remain constant. I did repeat some of the intervals, but not every time. I would also expect that either direction that the ramp was set up, the time intervals would also be the same. I must have altered the starting position of the ball slightly somehow when we turned the domino to the left side of the ramp.
All the standard physics laws apply for average velocity, and acceleration.
#$&*
Now place two dominoes under the right end and repeat the process, obtaining the time interval for each of 5 trials.
Then place the two dominoes under the left end and repeat once more.
Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.093
1
1.093
1.203
1.25
1.25
1.25
1.328
1.359
Similar results as with the one domino. For whatever reason, placing the domino under the right side of the ramp yields slightly faster time intervals. Again, all laws of physics apply. We know the distance and clock time and can calculate velocity, as well as acceleration.
#$&*
Repeat the preceding using 3 dominoes instead of 2. Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
#$&*
Repeat the preceding again, still using the 3 domino setup, but this time place a CD or a DVD disk (or something of roughly similar thickness) on the 'low' end of the ramp. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.203
1.063
1.188
1.156
The dominoes were on the left side of the ramp, the CD on the right on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the CD.
#$&*
Repeat the preceding one last time, still using the 3 domino setup, but remove the disk and replace it with a piece of paper. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.219
1.109
1.047
1.094
1.047
The dominoes were on the left side of the ramp, the piece of paper on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the piece of paper.
#$&*
Do your results support or fail to support the hypotheses you stated in the first two questions, regarding the relationship between time intervals and slopes? Explain.
Your answer (start in the next line):
My results from the data using the metal bracket during all three ramp heights supported my hypothesis that the higher the ramp the quicker the ball would roll down the distance of the ramp. For example with one domino on the left hand side of the ramp it took on average 1.647 seconds for the ball to roll down and hit the bracket. For three dominoes (higher ramp) it took on average .903 seconds for the ball to roll down and hit the bracket. This is .744 seconds faster for the higher ramp.
#$&*
How do you think the average velocity of the ball is related to the slope of the ramp? Explain in as much detail as possible.
Your answer (start in the next line):
Average velocity is defined by the change in distance/change in clock time. The distance the ball traveled was 33.6 cm, the change in time was 1.647 seconds (for one domino) because it started from rest.
Therefore the average velocity for the ramp with one domino = 33.6 cm/1.647 seconds = 20.4 cm/sec.
The average velocity for the ramp with three dominoes = 33.6 cm/.903 seconds = 37 cm/sec.
The velocity is therefore greater when the slope of the ramp is greater.
#$&*
Speculate on what it is that causes the average velocity on these ramps to change with slope.
Your answer (start in the next line):
Slope in general is defined as the change in y-axis value/change in x-axis value. If you are changing the y-value, the height of the slope using the dominoes, and not changing the run value or distance of the ramp, then as the slope will increase. As the slope increases so does the velocity of the ball rolling down the ramp. The slope on a distance vs. clock time graph gives you the average velocity of the object.
#$&*
How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
By calculating the velocity as I did in the previous questions it proved that the velocity of the higher ramp, 37 cm/s was more than the velocity of the lowest ramp, 20.4 cm/ s.
#$&*
Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp was slightly slower for the CD than the metal bracket. It was .903 sec for the bracket and 1.144 sec for the CD. I didn’t think there should be a difference, but however from the results, the disk did seem to make a difference, but very slightly.
#$&*
Do your data conclusively show that the piece of paper made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp with the bracket was .903 seconds and for the piece of paper, 1.103 seconds. Again, I didn’t think there should be a difference, but from the results, the paper also showed a slight difference from the bracket.
#$&*
Imagine that someone is placing different objects below the 'low' end of the ramp, and you are timing the ball. Assume that somehow the object placed below the 'low' end is hidden from you in a way that does not interfere with the timing process. Compared to the thickness of the DVD, how thin would the object have to be before you would be unable, using the TIMER, to observe a difference in times down the ramp?
Answer this question in the first line below. Express your answer in multiples or fractions of the thickness of a disk.
Starting in the second line, explain how you came to your conclusion, based on the results you obtained in this experiment. Also discuss how you could modify or refine the experiment, still using the TIMER, to distinguish the effect of the thinnest possible object placed under the 'low end.
Your answer (start in the next line):
2
Looking at the thickness of the metal bracket compared to the thickness of the CD used, I felt that the bracket was about twice as thick. The time interval recorded, on average, for the ball to completely roll down the ramp was .903 seconds and the CD again, 1.144 seconds. This is only a difference of .241 seconds. I felt like it was easier to click using the TIMER program when the ball reached the metal bracket because of the “bang” the ball makes with the metal. My reaction I feel is better than hearing the ball hit the CD.
To refine the experiment find a paper-thin piece of metal, similar to our metal strap used in the angular velocity experiment, and place at the end. Doing this you would have the combination of the sound and the thin material. This combination would help with the accuracy of the timed interval.
#$&*
Had you placed the disk below the 'low' end of the ramp in a 1-domino setup, do you think the difference in times would have been greater or less? Do you think you would be better able distinguish the presence of a thinner object using the 1-domino setup, or the 3-domino setup? Explain your reasoning below:
Your answer (start in the next line):
I think the times would have still been greater just because of the “sound” effect of the metal vs a CD or piece of paper - height wouldn’t matter in this case.
For the 1-domino vs 3-domino setup, a thinner object would be more distinguishable with the 3-domino because the ball is coming down the ramp at a greater velocity and force and hits the thinner object harder which is easier to distinguish in sound and with the naked eye.
#$&*
Does the ball's velocity change more or less quickly with the 3-domino setup or the 1-domino setup? Explain as best you can how you could use your results to support your answer.
Your answer (start in the next line):
With the ball starting from rest and time = 0, the average acceleration, or change in velocity of the 3-domino setup would be = (change in velocity)/(change in clock time) = (37 cm/sec - 0 m/s)/(.903 sec - 0) = 40.97 cm/s^2.
With the ball starting from rest and time = 0, the average acceleration of the 1-domino setup would be (20.4 cm/s - 0 cm/s)/(1.647 sec - 0 sec) = 12.39 cm/s^2.
The ball accelerating faster on the 3-domino setup.
#$&*
Your instructor is trying to gauge the typical time spent by students on these experiments. Please answer the following question as accurately as you can, understanding that your answer will be used only for the stated purpose and has no bearing on your grades:
• Approximately how long did it take you to complete this experiment?
Your answer (start in the next line):
1.5 hours
self-critique rating
#$&*
phy 231
Your 'ball down ramp' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
#$&* Your general comment **
July 4th, 6:22 pm
#$&* Will a steeper ramp give greater or lesser time? **
A ball is timed as it rolls from rest to the end of a ramp. The slope of the ramp is varied. Preliminary conclusions are drawn about the motion and the effect of ramp slope. A subsequent lab exercise uses the data from this lab to reach additional conclusions.
Most students report completion times between 45 minutes and 75 minutes hour, with a few reporting times as short as 25 minutes or as long as 2 hours. Median time of completion is around 1 hour.
Timing Ball down Ramp
The picture below shows a ball near the end of a grooved steel track (this steel track is a piece of 'shelf standard'); the shelf standard is supported by a stack of two dominoes. Your lab materials package contains two pieces of shelf standard; the shelf standard shown in the figure is white, but the one in your kit might be colored black, gold, silver or any of a variety of other colors.
If a ball rolls from an initial state of rest down three ramps with different slopes, the same distance along the ramp each time, do you think the time required to roll the length of the ramp will be greatest or least for the steepest ramp, or will the interval on the steepest ramp be neither the greatest nor the least? Explain why you think you have correctly predicted the behavior of the system.
Your answer (start in the next line):
I predict that the steeper the ramp the least time it will take for the ball to roll down that ramp. You are increasing the slope and therefore the ball will roll faster. The faster it rolls the quicker it gets down the ramp or the “least” time it will take.
#$&*
If we write down the slopes from least to greatest, next to the time intervals observed for those slopes, would you expect the time intervals to be increasing or decreasing, or do you think there would be no clear pattern? Explain why you think you have correctly described the behavior of the numbers in the table.
Your answer (start in the next line):
If the slopes are listed from least to greatest next to their corresponding time intervals, I would expect the time intervals to be decreasing. The reasoning is the same as the last question: the higher the slope the faster the ball will roll down, therefore the time will be the shortest on the greatest slope.
#$&*
Set up the shelf standard ramp on a reasonably level table, using a piece of 30-cm shelf standard and a single domino under the high end of the ramp. Position the dominoes so that the last .5 cm of the ramp extends beyond the point where the ramp contacts the domino,.and do the same in all subsequent setups.
Set the bracket on the table, touching the lower end of the ramp so that a ball rolling down the ramp will strike the bracket..
Mark a point about 3 cm below the top end of the ramp. Place a domino on the ramp to its high end is at this point, and place the ball just above the domino, so the domino is holding it back. Quickly pull the domino away from the ball so the ball begins to roll freely down the ramp. Allow the ball to roll until it strikes the bracket.
The bracket will probably move a little bit. Reset it at the end of the ramp.
Determine how far the ball rolled from release until it struck the bracket.
Now repeat, but this time use the TIMER. The first click will occur at the instant you release the ball, the second at the instant the ball strikes the bracket. Practice until you are as sure as you can be that you are clicking and pulling back the domino at the same instant, and that your second click is simultaneous with the ball striking the bracket.
When you are ready, do 5 trials 'for real' and record your time intervals.
Then reverse the system--without otherwise changing the position of the ramp, place the domino under the left end and position the bracket at the right end.
Time 5 trials with the ramp in this position.
In the space below, give the time interval for each trial, rounded to the nearest .001 second. Give 1 trial on each line, so that you will have a total of 10 lines, the first 5 lines for the first system, then 5 lines for the second system.
Beginning in 11th line give a short narrative description of what your data means and how it was collected.
Also describe what you were thinking, relevant to physics and the experiment, during the process of setting up the system and performing the trials.
Your answer (start in the next line):
1.625
1.703
1.625
1.703
1.58
2.047
2.016
1.984
2.016
2.031
If the conditions were perfect and the clicking of the TIMER at release and hitting the metal bracket were exact the time interval would remain constant. I did repeat some of the intervals, but not every time. I would also expect that either direction that the ramp was set up, the time intervals would also be the same. I must have altered the starting position of the ball slightly somehow when we turned the domino to the left side of the ramp.
All the standard physics laws apply for average velocity, and acceleration.
#$&*
Now place two dominoes under the right end and repeat the process, obtaining the time interval for each of 5 trials.
Then place the two dominoes under the left end and repeat once more.
Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.093
1
1.093
1.203
1.25
1.25
1.25
1.328
1.359
Similar results as with the one domino. For whatever reason, placing the domino under the right side of the ramp yields slightly faster time intervals. Again, all laws of physics apply. We know the distance and clock time and can calculate velocity, as well as acceleration.
#$&*
Repeat the preceding using 3 dominoes instead of 2. Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
#$&*
Repeat the preceding again, still using the 3 domino setup, but this time place a CD or a DVD disk (or something of roughly similar thickness) on the 'low' end of the ramp. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.203
1.063
1.188
1.156
The dominoes were on the left side of the ramp, the CD on the right on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the CD.
#$&*
Repeat the preceding one last time, still using the 3 domino setup, but remove the disk and replace it with a piece of paper. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.219
1.109
1.047
1.094
1.047
The dominoes were on the left side of the ramp, the piece of paper on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the piece of paper.
#$&*
Do your results support or fail to support the hypotheses you stated in the first two questions, regarding the relationship between time intervals and slopes? Explain.
Your answer (start in the next line):
My results from the data using the metal bracket during all three ramp heights supported my hypothesis that the higher the ramp the quicker the ball would roll down the distance of the ramp. For example with one domino on the left hand side of the ramp it took on average 1.647 seconds for the ball to roll down and hit the bracket. For three dominoes (higher ramp) it took on average .903 seconds for the ball to roll down and hit the bracket. This is .744 seconds faster for the higher ramp.
#$&*
How do you think the average velocity of the ball is related to the slope of the ramp? Explain in as much detail as possible.
Your answer (start in the next line):
Average velocity is defined by the change in distance/change in clock time. The distance the ball traveled was 33.6 cm, the change in time was 1.647 seconds (for one domino) because it started from rest.
Therefore the average velocity for the ramp with one domino = 33.6 cm/1.647 seconds = 20.4 cm/sec.
The average velocity for the ramp with three dominoes = 33.6 cm/.903 seconds = 37 cm/sec.
The velocity is therefore greater when the slope of the ramp is greater.
#$&*
Speculate on what it is that causes the average velocity on these ramps to change with slope.
Your answer (start in the next line):
Slope in general is defined as the change in y-axis value/change in x-axis value. If you are changing the y-value, the height of the slope using the dominoes, and not changing the run value or distance of the ramp, then as the slope will increase. As the slope increases so does the velocity of the ball rolling down the ramp. The slope on a distance vs. clock time graph gives you the average velocity of the object.
#$&*
How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
By calculating the velocity as I did in the previous questions it proved that the velocity of the higher ramp, 37 cm/s was more than the velocity of the lowest ramp, 20.4 cm/ s.
#$&*
Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp was slightly slower for the CD than the metal bracket. It was .903 sec for the bracket and 1.144 sec for the CD. I didn’t think there should be a difference, but however from the results, the disk did seem to make a difference, but very slightly.
#$&*
Do your data conclusively show that the piece of paper made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp with the bracket was .903 seconds and for the piece of paper, 1.103 seconds. Again, I didn’t think there should be a difference, but from the results, the paper also showed a slight difference from the bracket.
#$&*
Imagine that someone is placing different objects below the 'low' end of the ramp, and you are timing the ball. Assume that somehow the object placed below the 'low' end is hidden from you in a way that does not interfere with the timing process. Compared to the thickness of the DVD, how thin would the object have to be before you would be unable, using the TIMER, to observe a difference in times down the ramp?
Answer this question in the first line below. Express your answer in multiples or fractions of the thickness of a disk.
Starting in the second line, explain how you came to your conclusion, based on the results you obtained in this experiment. Also discuss how you could modify or refine the experiment, still using the TIMER, to distinguish the effect of the thinnest possible object placed under the 'low end.
Your answer (start in the next line):
2
Looking at the thickness of the metal bracket compared to the thickness of the CD used, I felt that the bracket was about twice as thick. The time interval recorded, on average, for the ball to completely roll down the ramp was .903 seconds and the CD again, 1.144 seconds. This is only a difference of .241 seconds. I felt like it was easier to click using the TIMER program when the ball reached the metal bracket because of the “bang” the ball makes with the metal. My reaction I feel is better than hearing the ball hit the CD.
To refine the experiment find a paper-thin piece of metal, similar to our metal strap used in the angular velocity experiment, and place at the end. Doing this you would have the combination of the sound and the thin material. This combination would help with the accuracy of the timed interval.
#$&*
Had you placed the disk below the 'low' end of the ramp in a 1-domino setup, do you think the difference in times would have been greater or less? Do you think you would be better able distinguish the presence of a thinner object using the 1-domino setup, or the 3-domino setup? Explain your reasoning below:
Your answer (start in the next line):
I think the times would have still been greater just because of the “sound” effect of the metal vs a CD or piece of paper - height wouldn’t matter in this case.
For the 1-domino vs 3-domino setup, a thinner object would be more distinguishable with the 3-domino because the ball is coming down the ramp at a greater velocity and force and hits the thinner object harder which is easier to distinguish in sound and with the naked eye.
#$&*
Does the ball's velocity change more or less quickly with the 3-domino setup or the 1-domino setup? Explain as best you can how you could use your results to support your answer.
Your answer (start in the next line):
With the ball starting from rest and time = 0, the average acceleration, or change in velocity of the 3-domino setup would be = (change in velocity)/(change in clock time) = (37 cm/sec - 0 m/s)/(.903 sec - 0) = 40.97 cm/s^2.
With the ball starting from rest and time = 0, the average acceleration of the 1-domino setup would be (20.4 cm/s - 0 cm/s)/(1.647 sec - 0 sec) = 12.39 cm/s^2.
The ball accelerating faster on the 3-domino setup.
#$&*
Your instructor is trying to gauge the typical time spent by students on these experiments. 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 experiment?
Your answer (start in the next line):
1.5 hours
self-critique rating
#*&!
#$&*
phy 231
Your 'ball down ramp' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
#$&* Your general comment **
July 4th, 6:22 pm
#$&* Will a steeper ramp give greater or lesser time? **
A ball is timed as it rolls from rest to the end of a ramp. The slope of the ramp is varied. Preliminary conclusions are drawn about the motion and the effect of ramp slope. A subsequent lab exercise uses the data from this lab to reach additional conclusions.
Most students report completion times between 45 minutes and 75 minutes hour, with a few reporting times as short as 25 minutes or as long as 2 hours. Median time of completion is around 1 hour.
Timing Ball down Ramp
The picture below shows a ball near the end of a grooved steel track (this steel track is a piece of 'shelf standard'); the shelf standard is supported by a stack of two dominoes. Your lab materials package contains two pieces of shelf standard; the shelf standard shown in the figure is white, but the one in your kit might be colored black, gold, silver or any of a variety of other colors.
If a ball rolls from an initial state of rest down three ramps with different slopes, the same distance along the ramp each time, do you think the time required to roll the length of the ramp will be greatest or least for the steepest ramp, or will the interval on the steepest ramp be neither the greatest nor the least? Explain why you think you have correctly predicted the behavior of the system.
Your answer (start in the next line):
I predict that the steeper the ramp the least time it will take for the ball to roll down that ramp. You are increasing the slope and therefore the ball will roll faster. The faster it rolls the quicker it gets down the ramp or the “least” time it will take.
#$&*
If we write down the slopes from least to greatest, next to the time intervals observed for those slopes, would you expect the time intervals to be increasing or decreasing, or do you think there would be no clear pattern? Explain why you think you have correctly described the behavior of the numbers in the table.
Your answer (start in the next line):
If the slopes are listed from least to greatest next to their corresponding time intervals, I would expect the time intervals to be decreasing. The reasoning is the same as the last question: the higher the slope the faster the ball will roll down, therefore the time will be the shortest on the greatest slope.
#$&*
Set up the shelf standard ramp on a reasonably level table, using a piece of 30-cm shelf standard and a single domino under the high end of the ramp. Position the dominoes so that the last .5 cm of the ramp extends beyond the point where the ramp contacts the domino,.and do the same in all subsequent setups.
Set the bracket on the table, touching the lower end of the ramp so that a ball rolling down the ramp will strike the bracket..
Mark a point about 3 cm below the top end of the ramp. Place a domino on the ramp to its high end is at this point, and place the ball just above the domino, so the domino is holding it back. Quickly pull the domino away from the ball so the ball begins to roll freely down the ramp. Allow the ball to roll until it strikes the bracket.
The bracket will probably move a little bit. Reset it at the end of the ramp.
Determine how far the ball rolled from release until it struck the bracket.
Now repeat, but this time use the TIMER. The first click will occur at the instant you release the ball, the second at the instant the ball strikes the bracket. Practice until you are as sure as you can be that you are clicking and pulling back the domino at the same instant, and that your second click is simultaneous with the ball striking the bracket.
When you are ready, do 5 trials 'for real' and record your time intervals.
Then reverse the system--without otherwise changing the position of the ramp, place the domino under the left end and position the bracket at the right end.
Time 5 trials with the ramp in this position.
In the space below, give the time interval for each trial, rounded to the nearest .001 second. Give 1 trial on each line, so that you will have a total of 10 lines, the first 5 lines for the first system, then 5 lines for the second system.
Beginning in 11th line give a short narrative description of what your data means and how it was collected.
Also describe what you were thinking, relevant to physics and the experiment, during the process of setting up the system and performing the trials.
Your answer (start in the next line):
1.625
1.703
1.625
1.703
1.58
2.047
2.016
1.984
2.016
2.031
If the conditions were perfect and the clicking of the TIMER at release and hitting the metal bracket were exact the time interval would remain constant. I did repeat some of the intervals, but not every time. I would also expect that either direction that the ramp was set up, the time intervals would also be the same. I must have altered the starting position of the ball slightly somehow when we turned the domino to the left side of the ramp.
All the standard physics laws apply for average velocity, and acceleration.
#$&*
Now place two dominoes under the right end and repeat the process, obtaining the time interval for each of 5 trials.
Then place the two dominoes under the left end and repeat once more.
Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.093
1
1.093
1.203
1.25
1.25
1.25
1.328
1.359
Similar results as with the one domino. For whatever reason, placing the domino under the right side of the ramp yields slightly faster time intervals. Again, all laws of physics apply. We know the distance and clock time and can calculate velocity, as well as acceleration.
#$&*
Repeat the preceding using 3 dominoes instead of 2. Enter your 10 time intervals using the same format as before.
Your answer (start in the next line):
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Repeat the preceding again, still using the 3 domino setup, but this time place a CD or a DVD disk (or something of roughly similar thickness) on the 'low' end of the ramp. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.109
1.203
1.063
1.188
1.156
The dominoes were on the left side of the ramp, the CD on the right on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the CD.
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Repeat the preceding one last time, still using the 3 domino setup, but remove the disk and replace it with a piece of paper. You need time only 5 intervals, but if you prefer you may use 10. Enter your 5 (or 10) time intervals using the same format as before.
Your answer (start in the next line):
1.219
1.109
1.047
1.094
1.047
The dominoes were on the left side of the ramp, the piece of paper on the lower end. The list above shows the results of 5 trials of the time it took for the ball to be released and hit the piece of paper.
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Do your results support or fail to support the hypotheses you stated in the first two questions, regarding the relationship between time intervals and slopes? Explain.
Your answer (start in the next line):
My results from the data using the metal bracket during all three ramp heights supported my hypothesis that the higher the ramp the quicker the ball would roll down the distance of the ramp. For example with one domino on the left hand side of the ramp it took on average 1.647 seconds for the ball to roll down and hit the bracket. For three dominoes (higher ramp) it took on average .903 seconds for the ball to roll down and hit the bracket. This is .744 seconds faster for the higher ramp.
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How do you think the average velocity of the ball is related to the slope of the ramp? Explain in as much detail as possible.
Your answer (start in the next line):
Average velocity is defined by the change in distance/change in clock time. The distance the ball traveled was 33.6 cm, the change in time was 1.647 seconds (for one domino) because it started from rest.
Therefore the average velocity for the ramp with one domino = 33.6 cm/1.647 seconds = 20.4 cm/sec.
The average velocity for the ramp with three dominoes = 33.6 cm/.903 seconds = 37 cm/sec.
The velocity is therefore greater when the slope of the ramp is greater.
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Speculate on what it is that causes the average velocity on these ramps to change with slope.
Your answer (start in the next line):
Slope in general is defined as the change in y-axis value/change in x-axis value. If you are changing the y-value, the height of the slope using the dominoes, and not changing the run value or distance of the ramp, then as the slope will increase. As the slope increases so does the velocity of the ball rolling down the ramp. The slope on a distance vs. clock time graph gives you the average velocity of the object.
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How might you verify whether your speculations are indeed valid explanations?
Your answer (start in the next line):
By calculating the velocity as I did in the previous questions it proved that the velocity of the higher ramp, 37 cm/s was more than the velocity of the lowest ramp, 20.4 cm/ s.
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Do your data conclusively show that the disk made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp was slightly slower for the CD than the metal bracket. It was .903 sec for the bracket and 1.144 sec for the CD. I didn’t think there should be a difference, but however from the results, the disk did seem to make a difference, but very slightly.
@& Whether this difference is significant basically depends on the standard deviation of your timing, and the number of trials.*@
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Do your data conclusively show that the piece of paper made a difference?
Your answer (start in the next line):
My data showed that the time interval for the ball to roll down the ramp with the bracket was .903 seconds and for the piece of paper, 1.103 seconds. Again, I didn’t think there should be a difference, but from the results, the paper also showed a slight difference from the bracket.
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Imagine that someone is placing different objects below the 'low' end of the ramp, and you are timing the ball. Assume that somehow the object placed below the 'low' end is hidden from you in a way that does not interfere with the timing process. Compared to the thickness of the DVD, how thin would the object have to be before you would be unable, using the TIMER, to observe a difference in times down the ramp?
Answer this question in the first line below. Express your answer in multiples or fractions of the thickness of a disk.
Starting in the second line, explain how you came to your conclusion, based on the results you obtained in this experiment. Also discuss how you could modify or refine the experiment, still using the TIMER, to distinguish the effect of the thinnest possible object placed under the 'low end.
Your answer (start in the next line):
2
Looking at the thickness of the metal bracket compared to the thickness of the CD used, I felt that the bracket was about twice as thick. The time interval recorded, on average, for the ball to completely roll down the ramp was .903 seconds and the CD again, 1.144 seconds. This is only a difference of .241 seconds. I felt like it was easier to click using the TIMER program when the ball reached the metal bracket because of the “bang” the ball makes with the metal. My reaction I feel is better than hearing the ball hit the CD.
To refine the experiment find a paper-thin piece of metal, similar to our metal strap used in the angular velocity experiment, and place at the end. Doing this you would have the combination of the sound and the thin material. This combination would help with the accuracy of the timed interval.
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Had you placed the disk below the 'low' end of the ramp in a 1-domino setup, do you think the difference in times would have been greater or less? Do you think you would be better able distinguish the presence of a thinner object using the 1-domino setup, or the 3-domino setup? Explain your reasoning below:
Your answer (start in the next line):
I think the times would have still been greater just because of the “sound” effect of the metal vs a CD or piece of paper - height wouldn’t matter in this case.
For the 1-domino vs 3-domino setup, a thinner object would be more distinguishable with the 3-domino because the ball is coming down the ramp at a greater velocity and force and hits the thinner object harder which is easier to distinguish in sound and with the naked eye.
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Does the ball's velocity change more or less quickly with the 3-domino setup or the 1-domino setup? Explain as best you can how you could use your results to support your answer.
Your answer (start in the next line):
With the ball starting from rest and time = 0, the average acceleration, or change in velocity of the 3-domino setup would be = (change in velocity)/(change in clock time) = (37 cm/sec - 0 m/s)/(.903 sec - 0) = 40.97 cm/s^2.
@& Right idea for the comparison.
You don't show the details, but I suspect your 37 cm/s might be the avearge velocity rather than the final velocity. If so the acceleration would be closer to 80 cm/s^2.*@
With the ball starting from rest and time = 0, the average acceleration of the 1-domino setup would be (20.4 cm/s - 0 cm/s)/(1.647 sec - 0 sec) = 12.39 cm/s^2.
The ball accelerating faster on the 3-domino setup.
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Your instructor is trying to gauge the typical time spent by students on these experiments. 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 experiment?
Your answer (start in the next line):
1.5 hours
self-critique rating
#*&!#*&!*#&!*#&!
&#Good responses on this lab exercise. See my notes and let me know if you have questions.
Revision isn't requested, but if you do choose to submit revisions, clarifications or questions, please insert them into a copy of this document, and mark your insertions with &&&& (please mark each insertion at the beginning and at the end).
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