course Mth 173
2/10 12:30
The problem: You don't have to actually do so, but it should be clear that if you wished to do so, you could take several
observations of positions and clock times. The main point here is to think about how you would use that
information if you did go to the trouble of collecting it. However, most students do not answer these questions in
terms of position and clock time information. Some students do not pause the video as instructed. To be sure you
are thinking in terms of positions and clock times, please take a minute to do the following, which should not take
you more than a couple of minutes:
Pick one of the videos, and write down the position and clock time of one of the objects, as best you can determine
them, in each of three different frames. The three frames should all depict the same 'roll' down the ramp, i.e.
the same video clip, at three different clock times. They should not include information from two or more
different video clips.
For each of the three readings, simply write down the clock time as it appears on the computer screen, and the
position of the object along the meter stick. You can choose either object (i.e., either the pendulum or the roll
of tape), but use the same object for all three measurements. Do not go to a lot of trouble to estimate the
position with great accuracy. Just make the best estimates you can in a couple of minutes.
Which object did you choose and what were the three positions and the three clock times?
answer/question/discussion (start in the next line):
In video 1 I used the roll of tape. 59.25, about 2 inches; 59.687, about 11 inches; 59.906, about 20 inches.
#$&*
In the following you don't have to actually do calculations with your actual data. Simply explain how you would
use data of this nature if you had a series of several position vs. clock time observations:
If you did use observations of positions and clock times from this video, how accurately do you think you could
determine the positions, and how accurately do you think you would know the clock times? Give a reasonable
numerical answer to this question (e.g., positions within 1 meter, within 2 centimeters, within 3 inches, etc;
clock times within 3 seconds, or within .002 seconds, or within .4 seconds, etc.). You should include an
explanations of the basis for your estimate: Why did you make the estimate you did?
answer/question/discussion (start in the next line):
Using this data you could determine the speed of the object, if given a specific time you could find the distance,
and if given a distance you could find the time. Clock times are very precise, within .002 seconds, as you are
looking at the timer reading all the way down to the thousandth of a second. The distance on video could vary
within about a half an inch, because of the camera angle, video quality, and pendulum sometimes blocking the view
of the tape.
#$&*
How can you use observations of position and clock time to determine whether the tape rolling along an incline is
speeding up or slowing down?
answer/question/discussion (start in the next line):
You would use certain time intervals from the video and observe the distance the object has travelled.
#$&*
How can you use observations of position and clock time to determine whether the swinging pendulum is speeding up
or slowing down?
answer/question/discussion (start in the next line):
Allowing the pendulum to swing back and forth over a certain period of time, you would use the distance travelled
in certain time periods.
#$&*
Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General
College Physics may do so but it is optional for these students): It is obvious that a pendulum swinging back and
forth speeds up at times, and slows down at times. How could you determine, by measuring positions and clock
times, at what location a swinging pendulum starts slowing down?
answer/question/discussion (start in the next line):
When it is speeding up the distance travelled will be greater over a period of time, and when slowing down the
distance travelled will be less. Using time intervals to determine distance travelled.
#$&*
Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General
College Physics may do so but it is optional for these students): How could you use your observations to determine
whether the rate at which the tape is speeding up is constant, increasing or decreasing?
answer/question/discussion (start in the next line):
Using certain time intervals you can distinguish the distance travelled in that time period. Then comparing this
data over several time periods using the distance travelled, and looking at successive time periods, you could
determine if it travelled farther or not as far. If the distance is continually getting larger over the time
periods, then it would be speeding up, if getting smaller it is slowing down, and if staying the same it would be
constant.
#$&*
Check to see that you have followed the instructions:
The instructions told you to pause the video multiple times. It appears that some students are not following this
instruction.
If you haven't used the 'pause' and 'play' buttons on your media player, you should go back and do so.
The questions are phrased to ask not only what you see when you play the video, but what you see when you pause the
video as instructed, and what you think you could determine if you were to actually take data from the video. You
aren't asked to actually take the data, but you need to answer how you would use it if you did.
It's OK if you have given more general descriptions, which are certainly relevant. But answers to the questions
should include an explanation of how you could use the series of position and clock time observations that are may
be observed with this video.
The questions also ask how much uncertainty there would be in the positions and clock times observable with this
specific video. Different people will have different answers, and some reasonable answers might vary from one clip
to the next, or from one part of a clip to another. However the answers should include a reasonable quantitative
estimate (i.e., numbers to represent the uncertainty; e.g., .004 seconds of uncertainty in clock times, 2 inches in
position measurements. Use your own estimates; neither of these example values is necessarily reasonable for this
situation). You should also explain the basis for your estimate: why did you make the estimate you did?
You should have estimated the number of seconds or fraction of a second to within which you think the time
displayed on the computer screen might be accurate (e.g., is it accurate to within 10 seconds of the actual clock
time, or to within 1 second, within .1 second, maybe even within .01 or .001 second). You might not yet know
enough about the TIMER to give an accurate answer, but give the best answer you can.
You should also indicate a reasonable estimate of the number of inches or fraction of an inch to within which you
could, if asked, determine the position of each object.
"
&#Your work looks good. Let me know if you have any questions. &#
course phy 121
2/10 12:30
The problem: You don't have to actually do so, but it should be clear that if you wished to do so, you could take several
observations of positions and clock times. The main point here is to think about how you would use that
information if you did go to the trouble of collecting it. However, most students do not answer these questions in
terms of position and clock time information. Some students do not pause the video as instructed. To be sure you
are thinking in terms of positions and clock times, please take a minute to do the following, which should not take
you more than a couple of minutes:
Pick one of the videos, and write down the position and clock time of one of the objects, as best you can determine
them, in each of three different frames. The three frames should all depict the same 'roll' down the ramp, i.e.
the same video clip, at three different clock times. They should not include information from two or more
different video clips.
For each of the three readings, simply write down the clock time as it appears on the computer screen, and the
position of the object along the meter stick. You can choose either object (i.e., either the pendulum or the roll
of tape), but use the same object for all three measurements. Do not go to a lot of trouble to estimate the
position with great accuracy. Just make the best estimates you can in a couple of minutes.
Which object did you choose and what were the three positions and the three clock times?
answer/question/discussion (start in the next line):
In video 1 I used the roll of tape. 59.25, about 2 inches; 59.687, about 11 inches; 59.906, about 20 inches.
#$&*
In the following you don't have to actually do calculations with your actual data. Simply explain how you would
use data of this nature if you had a series of several position vs. clock time observations:
If you did use observations of positions and clock times from this video, how accurately do you think you could
determine the positions, and how accurately do you think you would know the clock times? Give a reasonable
numerical answer to this question (e.g., positions within 1 meter, within 2 centimeters, within 3 inches, etc;
clock times within 3 seconds, or within .002 seconds, or within .4 seconds, etc.). You should include an
explanations of the basis for your estimate: Why did you make the estimate you did?
answer/question/discussion (start in the next line):
Using this data you could determine the speed of the object, if given a specific time you could find the distance,
and if given a distance you could find the time. Clock times are very precise, within .002 seconds, as you are
looking at the timer reading all the way down to the thousandth of a second. The distance on video could vary
within about a half an inch, because of the camera angle, video quality, and pendulum sometimes blocking the view
of the tape.
#$&*
How can you use observations of position and clock time to determine whether the tape rolling along an incline is
speeding up or slowing down?
answer/question/discussion (start in the next line):
You would use certain time intervals from the video and observe the distance the object has travelled.
#$&*
How can you use observations of position and clock time to determine whether the swinging pendulum is speeding up
or slowing down?
answer/question/discussion (start in the next line):
Allowing the pendulum to swing back and forth over a certain period of time, you would use the distance travelled
in certain time periods.
#$&*
Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General
College Physics may do so but it is optional for these students): It is obvious that a pendulum swinging back and
forth speeds up at times, and slows down at times. How could you determine, by measuring positions and clock
times, at what location a swinging pendulum starts slowing down?
answer/question/discussion (start in the next line):
When it is speeding up the distance travelled will be greater over a period of time, and when slowing down the
distance travelled will be less. Using time intervals to determine distance travelled.
#$&*
Challenge (University Physics students should attempt answer Challenge questions; Principles of Physics and General
College Physics may do so but it is optional for these students): How could you use your observations to determine
whether the rate at which the tape is speeding up is constant, increasing or decreasing?
answer/question/discussion (start in the next line):
Using certain time intervals you can distinguish the distance travelled in that time period. Then comparing this
data over several time periods using the distance travelled, and looking at successive time periods, you could
determine if it travelled farther or not as far. If the distance is continually getting larger over the time
periods, then it would be speeding up, if getting smaller it is slowing down, and if staying the same it would be
constant.
#$&*
Check to see that you have followed the instructions:
The instructions told you to pause the video multiple times. It appears that some students are not following this
instruction.
If you haven't used the 'pause' and 'play' buttons on your media player, you should go back and do so.
The questions are phrased to ask not only what you see when you play the video, but what you see when you pause the
video as instructed, and what you think you could determine if you were to actually take data from the video. You
aren't asked to actually take the data, but you need to answer how you would use it if you did.
It's OK if you have given more general descriptions, which are certainly relevant. But answers to the questions
should include an explanation of how you could use the series of position and clock time observations that are may
be observed with this video.
The questions also ask how much uncertainty there would be in the positions and clock times observable with this
specific video. Different people will have different answers, and some reasonable answers might vary from one clip
to the next, or from one part of a clip to another. However the answers should include a reasonable quantitative
estimate (i.e., numbers to represent the uncertainty; e.g., .004 seconds of uncertainty in clock times, 2 inches in
position measurements. Use your own estimates; neither of these example values is necessarily reasonable for this
situation). You should also explain the basis for your estimate: why did you make the estimate you did?
You should have estimated the number of seconds or fraction of a second to within which you think the time
displayed on the computer screen might be accurate (e.g., is it accurate to within 10 seconds of the actual clock
time, or to within 1 second, within .1 second, maybe even within .01 or .001 second). You might not yet know
enough about the TIMER to give an accurate answer, but give the best answer you can.
You should also indicate a reasonable estimate of the number of inches or fraction of an inch to within which you
could, if asked, determine the position of each object.
&#Good responses. Let me know if you have questions. &#