Asst 0

course PHY 121

CvϘLw~assignment #000

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000. `Query 0

Physics I

02-11-2008

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14:11:00

The Query program normally asks you questions about assigned problems and class notes, in question-answer-self-critique format. Since Assignments 0 and 1 consist mostly of lab-related activities, most of the questions on these queries will be related to your labs and will be in open-ended in form, without given solutions, and will not require self-critique.

The purpose of this Query is to gauge your understanding of some basic ideas about motion and timing, and some procedures to be used throughout the course in analyzing our observations. Answer these questions to the best of your ability. If you encounter difficulties, the instructor's response to this first Query will be designed to help you clarify anything you don't understand. {}{}Respond by stating the purpose of this first Query, as you currently understand it.

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RESPONSE -->

ok

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14:12:06

If, as in the object-down-an-incline experiment, you know the distance an object rolls down an incline and the time required, explain how you will use this information to find the object 's average speed on the incline.

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RESPONSE -->

Average speed is calculated by taking the distance of the incline and dividing it by the time taken to move down the incline.

AS = D / T

confidence assessment: 3

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14:14:14

If an object travels 40 centimeters down an incline in 5 seconds then what is its average velocity on the incline? Explain how your answer is connected to your experience.

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RESPONSE -->

average velocity = d/t

therefore,

40 cm / 5 s

= 8 cm/s

for each trial, i calculated the average velocity and compared the data from each trial.

confidence assessment: 2

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14:19:33

If the same object requires 3 second to reach the halfway point, what is its average velocity on the first half of the incline and what is its average velocity on the second half?

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RESPONSE -->

If it took 3 s out of 5 s total...

then

3s for 1st half and

2s for the 2nd half

and 1/2 of the 40 cm = 20 cm

therefore,

20 cm/3s = 6.7 cm/s 1st half

and

20cm/2s = 10 cm/s 2nd half

confidence assessment: 2

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14:24:26

Using the same type of setup you used for the first object-down-an-incline lab, if the computer timer indicates that on five trials the times of an object down an incline are 2.42 sec, 2.56 sec, 2.38 sec, 2.47 sec and 2.31 sec, then to what extent do you think the discrepancies could be explained by each of thefollowing: {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse){}{}c. Actual differences in the time required for the object to travel the same distance.{}{}d. Differences in positioningthe object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.

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RESPONSE -->

a. possible, however it is calculating to the .01 s and that is resonably accurate.

b. possible, but again the times are very resonable. but it was very hard to watch the release and end and click the mouse at the same time.

c. not possbile. if realeased at the same point every time the time should not vary too much as long as their are no outside factors.

d. very possible! i noticed that if i didn't release it at the same point it would affect the overall time.

confidence assessment: 2

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14:27:56

How much uncertainty do you think each of the following would actually contribute to the uncertainty in timing a number of trials for the object-down-an-incline lab? {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated bLine$(lineCount) =with an actual human finger on a computer mouse){}{}c. Actual differences in the time required for the object to travel the same distance.{}{}d. Differences in positioning the object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.

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RESPONSE -->

a. would be the same as the first. precise measurements.

b.very possible. esp for repeated trials.

c. not possible. should remain the same as long as a materials constant.

d. possible. haste makes waste.

d. very possible if you didn't clearly mark the end. and hard to click and watch at the same time.

confidence assessment: 2

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14:30:48

What, if anything, could you do about the uncertainty due to each of the following? Address each specifically. {}{}a. The lack of precision of the TIMER program{}{}b. The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse){}{}c. Actualdifferences in the time required for the object to travel the same distance.{}{}d. Differences in positioning the object prior to release.{}{}e. Human uncertainty in observing exactly when the object reached the end of the incline.

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RESPONSE -->

a. makes sure it is reporting to several decimal places accurately.

b. get a partner to help with start and finish observations.

c. shouldn't. if so you are releasing inaccurately each time.

d. make a lever to aid in release so that it is consistent each time.

e.use a partner as above.

confidence assessment: 2

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14:33:34

According to the results of your introductory pendulum experiment, do you think doubling the length of the pendulum will result in half the frequency (frequency can be thought of as the number of cycles per minute), more than half or less than half?

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RESPONSE -->

It would result in half the frequency because in the experiment i noticed that the greater the length of string the fewer oscillations or cycles per minute.

confidence assessment: 2

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14:34:26

Note that for a graph of y vs. x, a point on the x axis has y coordinate zero and a point on the y axis has x coordinate zero. In your own words explain why this is so.

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RESPONSE -->

i am not sure... but i believe it is because the line crosses or touches the graph at that point?

confidence assessment: 1

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14:36:42

On a graph of frequency vs. pendulum length (where frequency is on the vertical axis and length on the horizontal), what would it mean for the graph to intersect the vertical axis (i.e., what would it mean, in terms of the pendulum and its behavior, if the line or curve representing frequency vs. length goes through the vertical axis)? What would this tell you about the length and frequency of the pendulum?

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RESPONSE -->

?? that the frequency was decreasing if it crossed the vertical axis.

This would tell you that as length increases frequency decreases.

confidence assessment: 2

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14:37:50

On a graph of frequency vs. pendulum length, what would it mean for the graph to intersect the horizontal axis (i.e., what would it mean, in terms of the pendulum and its behavior, if the line or curve representing frequency vs. length goes through the horizontal axis)? What would this tell you about the length and frequency of the pendulum?

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RESPONSE -->

the same as before... that the frequency would be decreasing?

confidence assessment: 1

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14:46:19

If a ball rolls down between two points with an average velocity of 6 cm / sec, and if it takes 5 sec between the points, then how far apart are the points?

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RESPONSE -->

ok so the ball travels 6 cm every 1 s

therefore,

6 * 5 = 30 cm apart

confidence assessment: 2

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14:46:40

On the average the ball moves 6 centimeters every second, so in 5 seconds it will move 30 cm. {}{}The formal calculation goes like this: {}{}We know that vAve = `ds / `dt, where vAve is ave velocity, `ds is displacement and `dt is the time interval. {}It follows by algebraic rearrangement that `ds = vAve * `dt.{}We are told that vAve = 6 cm / sec and `dt = 5 sec. It therefore follows that{}{}`ds = 6 cm / sec * 5 sec = 30 (cm / sec) * sec = 30 cm.{}{}The details of the algebraic rearrangement are asfollows:{}{}vAve = `ds / `dt. We multiply both sides of the equation by `dt:{}vAve * `dt = `ds / `dt * `dt. We simplify to obtain{}vAve * `dt = `ds, which we then write as{}`ds = vAve *`dt.{}{}Be sure to address anything you do not fully understand in your self-critique.

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RESPONSE -->

great!

self critique assessment: 3

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14:50:40

You were asked to read the text and some of the problems at the end of the section. Tell me about something in the text you understood up to a point but didn't understand fully. Explain what you did understand, and ask the best question you can about what you didn't understand.

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RESPONSE -->

Chapter 1 and the resulting problems were easily understandable. It was very similar to what i teach in the first few chapters of Physical Science to my students.

I forgot about scientific notation but had to review that for the Astronomy class i am also taking. The conversions i don't do in teaching at this level with my students so i had to review that as well but it seems very familiar to me after a short review.

confidence assessment: 3

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Tell me about something in the problems you understand up to a point but don't fully understand. Explain what you did understand, and ask the best question you can about what you didn't understand.

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RESPONSE -->

I understand all but question 12. What does it mean by writing it in full decimal numbers with standard units?

confidence assessment:

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"

For example

4.53 gigawatts would be 4,530,000,000 watts

183 nanometers would be 183 * 10^-9 meters = .000000183 meters.

Good work. Let me know if you have additional questions.