#$&*
Phy 121
Your 'initial timing experiment' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Initial Timing Experiment_labelMessages **
** **
Copy this document, from this point to the end, into a word processor or text editor.
Follow the instructions, fill in your data and the results of your analysis in the given format.
Regularly save your document to your computer as you work.
When you have completed your work:
Copy the document into a text editor (e.g., Notepad; but NOT into a word processor or html editor, e.g., NOT into Word or FrontPage).
Highlight the contents of the text editor, and copy and paste those contents into the indicated box at the end of this form.
Click the Submit button and save your form confirmation.
Note: The majority of student report taking less than an hour on this experiment, though a few report significantly longer times.
Take reasonable care to get good data in this experiment. Try to do the timing as accurately as possible. Measurements of length, height, etc. should be reasonably
accurate (e.g., with a meter stick or ruler you can measure to withing +- 1 millimeter, but it's not necessary to try to determine fractions of a millimeter).
In this experiment you will use the TIMER program, a hardcover book, the toy car that came in your lab materials package (or, if you do not yet have the package, a
cylinder or some other object that will roll along the book in a relatively straight line), and a ruler or the equivalent (if you don't have one, note the Rulers link, which is
also given on the Assignments page).
The book's cover should be straight and unbent.
The toy car (or other object) should roll fairly smoothly.
Place the book on a flat level tabletop. You will prop one end of the book up a little bit, so that when it is released the object will roll without your assistance,
gradually speeding up, from the propped-up end to the lower end. However don't prop the end up too much. It should take at least two seconds for the ball to roll
down the length of the book when it is released from rest. For a typical book, a stack of two or three quarters placed under one end works well.
Using the TIMER program determine how long it takes the ball to roll from one end of the ramp to the other, when released from rest. Once you've got the book set
up, it takes only a few seconds to do a timing, so it won't take you long to time the object's motion at least three times.
Determine how far the object travels as it rolls from its initial position (where you first click the timer) to its final position (where you click at the end of the interval). This
will probably be a bit less than the length of the book, due to the length of the object itself.
Determine how much higher one end of the book was than the other, and how far it is from the supports (e.g., the stack of quarters, or whatever you used to support
one end) to the end of the book which rests on the table.
Then reverse the direction of the book on the tabletop, rotating the book an its supports (e.g., the stack of quarters) 180 degrees so that the ball will roll in exactly the
opposite direction. Repeat your measurements.
In the box below describe your setup, being as specific as possible about the book used (title, ISBN) and the object being used (e.g., a can of vegetables (full or
empty; should be specified) or a jar (again full or empty); anything round and smooth that will upon release roll fairly slowly down the incline), and what you used to
prop the object up (be as specific as possible). Also describe how well the object rolled--did it roll smoothly, did it speed up and slow down, did it roll in a straight
line or did its direction change somewhat?
your brief discussion/description/explanation:
I constructed my ramp out of my 6th edition 'Physics' textbook by Giancoli, ISBN: 0-13-060620-0 on my dining room table, a relatively level and flat surface. The
length of the ramp was 26 cm (206mm). At the starting place of rest, the ramp measured 47mm high off the table surface, and 41mm at the finish place, an overall
difference of 6mm. To establish the height of the ramp, I used a stack of 3 quarters (USD), which when measured aproximately 6mm.
A car was not included with my materials, so I used a 1 inch wooden dowel made of Poplar wood for my rolling object. The dowel measured 25mm in diam. and
76mm in length. The surface of the dowel was smoothly sanded and as Poplar is a fairly dense and closed grain wood, rolled well and evenly.
#$&* (note that your answer should always start in one of the blank lines preceding the #$&* mark)
In the space indicated below report your data. State exactly what was measured, how it was measured, how accurately you believe it was measured and of course
what the measurements were. Try to organize your report so the reader can easily scan your data and identify any patterns or trends.
your brief discussion/description/explanation:
I timed the object using small book as a starting gate at 0mm on the ruler and had the ruler stop at the edge of the book at 26mm. I placed a stack of magazines at the
end of the textbook so as to allow the dowel to roll past the 26mm mark for measurment purposes. I set my metric ruler lengthwise down the ramp, so I could align the
starting gate (book) and also sight the finish so I could stop the timer at the same moment for each consecutive attempt. I believe my experiment was conducted in a
manner that would give the least variables possible with each attempt. Without a mechanized starting gate and weight sensing finish timer, it is impossible to get an
exact reading each time, though I believe given human error the readings below were accurately found.
My Timer results for the first direction were as follows:
1 643.0254 643.0254
2 645.0231 2.177734
1 1026.855 1026.855
2 1029.068 2.212891
1 1266.996 1266.996
2 1269.246 2.25
For the opposite direction the results were:
1 1451.783 1451.783
2 1453.914 2.130859
1 1522.25 1522.25
2 1525.084 2.833984
1 1656.225 1656.225
2 1658.502 2.277344
#$&*
Using your data determine how fast the object was moving, on the average, as it rolled down the incline. Estimate how accurately you believe you were able to
determine the object's average speed, and give the best reasons you can for your estimate of the accuracy.
your brief discussion/description/explanation:
For the first direction, I calculated the dowel traveled at rates of 26cm/2.177sec=0.11939m/sec; 26cm/2021289sec=0.11749m/sec; and
26cm/2.25sec=0.11556m/sec. The vAve for all three readings was 0.11748m/sec.
For the measurements in the opposite direction I calculated: 26cm/2.130859sec=0.122m/sec; 26cm/2.83398=0.0917m/sec; and 26cm/2.77344sec=0.09375m/sec.
The combined vAve for the opposite direction readings was 0.102m/sec.
The difference in the two v Ave results of 0.11748m/sec. and 0.102m/sec is 0.01548, which suggests there may have been a discrepancy such as release time of the
starting gate, the levelness of the table surface, the levelness of the ramp in one direction as opposed to the other, or a combination of all of these factors. I believe
human error is also a possiblility, if it took longer to click the start/stop of the timer from one reading to the next.
#$&*
How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?
your brief discussion/description/explanation:
The object was at rest at the beginning of the timed interval, so the vAve was 0m/sec. I know this because the first reading for each timing the time split of the first
reading was the same as the first reading. The speed was greater at the lower end of the book than at the higher end.
#$&*
List the following in order, from least to greatest. Indicate 'ties': The object's initial speed, its final speed, its average speed, and the change in its speed as it rolled
from one end of the book to the other.
your brief discussion/description/explanation:
The object's intitial speed, the object's changed speed as it rolled from one end to the other which results in the average speed, and it's final speed which is the greatest.
#$&*
Devise and conduct an experiment to determine whether or not the object is speeding up as it rolls down the incline. If you have set the experiment up as indicated, it
should seem pretty obvious that the object is in fact speeding up. But figure out a way to use actual measurements to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how your data support your conclusions.
your brief discussion/description/explanation:
My new experiment was conducted with the same ramp as before: the Physics textbook, a stack of three quarters, the 26cm length, and the poplar wooden dowel as
before. For this experiment I added a marker at the 13cm, halfway point, and clicked the timer at this point as well.
By collecting three readings instead of only two, I am able to show the increase in velocity, as the object is rolling slower for the first half of the ramp than the second
half.
My results were:
1 6329.344 6329.344
2 6330.861 1.517578
3 6331.316 .4550781
I can see just by observing the timer results that the time the object took to travel the first 13cm is more than the time is took to travel the final 13mm, 1.517578sec. as opposed to 0.4550781sec for the final leg.
The vAve for the first 13cm is 13cm/1.517578sec=0.0856628m/sec. and the vAve for the final 13cm/.4550781=0.285665m/sec. I calculated a total vAve of 0.131846m/sec.
#$&*
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?
120minutes: 30 minutes for experiment and data collection, 50 minutes for extrapolation and qa.
#$&*
You may also include optional comments and/or questions.
#$&*
*#&!
&#Very good data and responses. Let me know if you have questions. &#