#$&*
PHY 241
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.
** **
** **
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 propped the book “Classic Airplanes” written by Walter J. Boyne up with four quarters which made the height 8mm. The distance between the support and the opposite end of the book was 298 mm. I used a hot wheels toy model of a yellow Lamborghini Gallardo. The car had a wheel base of 42mm. When released the car rolled smoothly in a fairly straight line down the incline appearing to increase speed at a constant rate. The timing of the trials was collected using the TIMER program and measurements were collected using a Fiskars wooden ruler.
#$&* (note that your answer should always start in one of the blank lines preceding the #$&* mark)
In the space indicated below report your data. State exactly what was measured, how it was measured, how accurately you believe it was measured and of course what the measurements were. Try to organize your report so the reader can easily scan your data and identify any patterns or trends.
your brief discussion/description/explanation:
Incline position Trial Time(s) Distance rolled(mm)
1 1 2.558594 270
1 2 2.542969 268
1 3 2.355469 295
2 1 2.480468 261
2 2 2.513069 271
2 3 2.480469 269
The time was measured from when the car was released to the time it came to a stop by the use of the TIMER program. I believe I calculated the time to within .01 seconds accurately.
The distance was measured from the intial position of the rear tire to the final position of the rear tire by the use of the Fiskars wooden ruler. I believe I calculated the distance traveled to within 1mm.
#$&*
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:
The object was moving on an average 109.6102 mm/s. I believe this is accurate to .001mm/s because I rounded to the ten-thousandths which could combined add or subtract .001 mm/s to the given average speed.
#$&*
How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?
your brief discussion/description/explanation:
The object was not moving at the beginning of the interval. The average speed during this interval was 109.6102 mm/s. I believe the object was traveling faster than the average speed at the lower end of the book because it takes into account the initial speed of 0 while the speed at the lower end is a buildup of all of the force from the beginning.
#$&*
@& Your individual timings differ from the mean by a few hundredths of a second, and the TIMER records time in intervals of about .01 second.
So 109.6102 mm / s has way too many significant figures.
Basically your mean time could possibly be accurate to within +- 1%, provided no systematic human error is present. So 109 mm/s might be valid, but any additional significant figures are superfluous and could be misleading.*@
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:
Final speed> change in speed> average speed> initial speed
#$&*
@& You would normally need to justify this, but it's accurate and I'm pretty confident you know why.*@
Devise and conduct an experiment to determine whether or not the object is speeding up as it rolls down the incline. If you have set the experiment up as indicated, it should seem pretty obvious that the object is in fact speeding up. But figure out a way to use actual measurements to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how your data support your conclusions.
your brief discussion/description/explanation:
I constructed a ramp using the book used before but this time increased the incline to 16 mm in height and ran the experiment as before. I then increased the incline to 24 mm in height and ran the experiment once again.
Incline height(mm) Trial Time(s) Distance(mm)
16 1 1.542969 298
2 1.542969 298
3 1.542699 298
24 1 1.027344 298
2 1.027296 298
3 1.027401 298
As the incline increased in height the time it took for the car to travel from one end to the next decreased, therefore indicating that the speed was increasing as the car traveled down the incline.
#$&*
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?
1 hour
#$&*
You may also include optional comments and/or questions.
#$&*
*#&!
@& Good, but check my notes, especially on significant figures.*@