#$&*
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 **
** **
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 used my cell biology book, The Cell(ISBN unknown) and one of my son's matchbox cars. The car is approximately 80mm long(weight unknown). I used three another toy to prop the book up at a height of approximately 40mm. The car rolled smoothly down the book as soon as I released it.
#$&* (note that your answer should always start in one of the blank lines preceding the #$&* mark)
In the space indicated below report your data. State exactly what was measured, how it was measured, how accurately you believe it was measured and of course what the measurements were. Try to organize your report so the reader can easily scan your data and identify any patterns or trends.
your brief discussion/description/explanation:
Trial Time Displacement
1 1.1 sec 204 mm
2 1.0 sec 204 mm
3 1.1 sec 204 mm
#$&*
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:
.204m/1.06sec=0.200 m/s When I released the car, it rolled on average 0.200 meters every second over the .204 meter cover. I would estimate my accuracy at 75%, with the limiting factor being that I had to release the car AND start the timer at the same time, using different hands. One major limitation is my timing(doing two things at once).
#$&*
How fast was the object moving at the beginning of the timed interval?
According to your previous calculation, what was its average speed during this interval?
Do you think the object, when it reached the lower end of the book, was moving at a speed greater or less than the average speed you calculated?
your brief discussion/description/explanation:
The object was at rest at the beginning of the time interval so it was moving at 0 m/s. The average speed was 0.2 m/s during the interval. It was probably moving at a greater rate of speed because it was still on an incline.
#$&*
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:
Initial speed
average speed ties change in its speed as its moving
final speed
#$&*
Devise and conduct an experiment to determine whether or not the object is speeding up as it rolls down the incline. If you have set the experiment up as indicated, it should seem pretty obvious that the object is in fact speeding up. But figure out a way to use actual measurements to support your belief.
Explain how you designed and conducted your experiment, give your data and explain how your data support your conclusions.
your brief discussion/description/explanation:
My family goes next door to visit my wife's grandmother from time to time. There is a considerable incline from our driveway to hers, and it's straight. I positioned my truck pointing down the hill and put it in neutral. At rest with my foot on the brake, my speed is zero miles per hour. When I release the brake, both my odometer and my speedometer increases(but not seemingly at the same rate). I reach 5 miles per hour fairly slowly but as I get further and further from my driveway(and closer to her house) my speed increases faster and faster(because I'm still on the incline). By the time I'm at her house, my odometer doesn't record very small increments, but I can estimate that the distance is approximately 300 feet. At the point where I cross her driveway, I'm traveling approximately 25 miles per hour. My watch(Tag Heuer Chronograph) reads 8.3 seconds. 300.0feet/8.300sec=36.14 ft/sec I obviously wasn't traveling at this rate the moment I removed my foot from the brake, so I must have been gaining speed as I moved down the hill.
#$&*
@&
Good.
I don't know what sort of surface your driveway has, but if it's smooth your results would be consistent with a slope of around 14%. That's fairly steep.
You'll understand later in the course how this estimate came about.
*@
*#&!*#&!
&#Your work on this lab exercise looks very good. Let me know if you have any questions. &#