initial timing experiment

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Phy 201

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.

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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 an eleven inch exercise physiology book entitled “Exercise Physiology: Theory and application to fitness and performance”, by Powers and Howley, ISBN number 978-0-07-337647-9, hard back, with piece of metal to prop up the higher end. I used the smaller marble that was included in our initial lab materials packet for the rolled object. The marble rolled in a relatively straight line for all three trials.

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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 measured everything with a tape measure that had markings down to the millimeter. I think my measurements were fairly accurate.

For the first direction:

Height from table to top of book on high end - 35mm

Height from table to top of book on low end - 31mm

Measured distance the marble traveled - .26m

Interval times:

1. 2sec

2. 1.984375sec

3. 2.3125sec

Opposite direction:

Height from table to top of book on high end - 35mm

Height from table to top of book on low end - 31mm

Measured distance the marble traveled - .26m

Interval times:

1. 3.328125sec

2. 2.65625sec

3. 2.46875sec

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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 facing the first direction the object was moving on average at .124m/sec. For the opposite direction is was moving an average of .281m/sec. I believe this is accurate because I found the velocity of the marble for each trial and then averaged them.

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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:

I do not believe the marble was moving much at all when I first started the timed interval. The average speed I calculated was .124m/sec and I think it would have been moving at a greater speed than the average I calculated.

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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 tied with change in speed

final speed

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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 taped a piece of printer paper to the top of the book so it wouldn’t slide. Then I marked off three 7cm segments; one at the beginning of the roll, the middle, and the end. I started the marble from the very first line of the first segment and timed how long it took the marble to complete the first segment. Then I started the marble from the same place but waited to start the timer til it got to the beginning of the second 7cm segment and stopped the timer when it reached the end of that segment. I then started the marble from the same starting spot but waited to start the timer til it reached the beginning of the last segment. Using the clocked intervals and distances I can calculate the average speed of the marble in each particular segment.

Segment 1. 1.328125sec

.07m/1.328125sec = .0527m/sec

Segment 2. .34375sec

.07m/ .34375sec = .2036m/sec

Segment 3. .203125sec

.07m/.203125sec = .3446m/sec

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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?

1 ½ hrs

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You may also include optional comments and/or questions.

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&#Very good data and responses. Let me know if you have questions. &#