query 0

course Phy231

}v׎Thǿ{ąJassignment #000

000. `Query 0

Physics I

01-30-2009

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19:09:11

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 -->

Check my knowledge of labs and basic ideas.

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19:09:32

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 -->

avg speed = distance traveled / time

confidence assessment: 3

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19:10:34

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 -->

40cm/5s=8cm/s

confidence assessment: 3

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19:11:53

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 -->

20cm/3s=6.3cm/s

20cm/2s=10cm/s

confidence assessment: 3

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19:20:10

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. The timer program would add about 0.01s error.

b. I would guess human triggering would add about 0.5 s error

c. This would contribute the most to the result.

d. I would guess the error in positioning to be at most +/-1 mm, so this would have a negligble effect on the result.

e. I would guess human observation would add another 0.5 s to the error.

confidence assessment: 2

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19:24:11

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. Use a more accurate timing device.

b. Design an experiment where there is no need to click the timer. (Such as making a video)

c. Use the same object.

d. This contributes the least to the error, but could be isoltated by the design of an apparatus to position the ball at the same point.

e. This could be isolated by better experiment design. (Such as using a video)

confidence assessment: 3

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19:26:17

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 -->

Doubling the length of the pendulum results in a cycles per min decrease that is more than half the previous value.

confidence assessment: 3

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19:26:56

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 -->

Point on x-axis has y value 0.

Point on y-axis has x value 0.

confidence assessment: 3

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19:28:32

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 as the length of the pendulum approaches 0, the frequency approaches infinity.

confidence assessment: 3

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19:29:16

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 -->

As pendulum length approaches infinity, the frequency approaches 0

confidence assessment: 3

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19:29:42

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 -->

D=RT

6cm/s*5s=30cm

confidence assessment: 3

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19:29:59

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 -->

self critique assessment: 3

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19:36:04

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 don't understand how in 1.15 I am suppose to know the percent error of a chemical balance and stopwatch without it being provided.

I don't understand how percent error is calculated for the solution when complex operations are involved such as multiplication as in 1.16

confidence assessment: 3

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&#Your work looks very good. Let me know if you have any questions. &#