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course phy 201
Question: This question, related to the use of the TIMER program in an experimental situation, is posed in terms of a familiar first-semester system.
Suppose you use a computer timer to time a steel ball 1 inch in diameter rolling down a straight wooden incline about 50 cm long. If the computer timer indicates that on five trials the times of an object down an incline are 2.42sec, 2.56 sec, 2.38 sec, 2.47 sec and 2.31 sec, then:
Are the discrepancies in timing on the order of 0.1 second, 0.01 second, or 0.001 second?
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To what extent do you think the discrepancies in the time intervals could be explained by each of the following:
· The lack of precision of the TIMER program. Base your answer on the precision of the TIMER program as you have experienced it. What percent of the discrepancies in timing do you think are due to this factor, and why do you think so?
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I don't think it lacks much precision I think it rounded around .001 but definitely not .1
From data given from the timer program
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· The uncertainty associated with human triggering (uncertainty associated with an actual human finger on a computer mouse). What percent of the discrepancies in timing do you think are due to this factor, and why do you think so?
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This could play a large factor possibly up to .5 seconds or more depending on the person
Our reflexes just aren't perfect
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· Actual differences in the time required for the object to travel the same distance. What percent of the discrepancies in timing do you think are due to this factor, and why do you think so?
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This could also be contributed to human error on how we replace the ball or accidently moving
the piece its on that is the reason
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· Differences in positioning the object prior to release. What percent of the discrepancies in timing do you think are due to this factor, and why do you think so?
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This I think could attribute to around .1 or below difference
I am not sure but I do know it would cause some difference in time
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· Human uncertainty in observing exactly when the object reached the end of the incline. What percent of the discrepancies in timing do you think are due to this factor, and why do you think so?
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Human error would be attributed to most if not all of the time difference we just can't measure
perfectly
It's just a human flaw to be imperfect
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Question: If you had carefully timed the ball and obtained the results given above, how confident would you be that the mean of those five intervals was within 0.1 seconds of the actual mean? (Note that the mean of the given intervals is 2.43 seconds, as rounded to three significant figures)? Briefly explain your thinking.
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very
The maximum differece between them all was a little more than .1 seconds so it is close
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How confident would you be that the 2.43 second mean is within .01 second? Briefly explain your thinking.
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Not very
The difference between some of them was .1 or more which is much more than .01
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How confident would you be that the 2.43 second mean is within .03 second?
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Still not confident
For the same reason as above
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At what level do you think you can be confident of the various degrees of uncertainty?
Do you think you could be 90% confident that the 2.43 second mean is within 0.1 second of the actual mean?
Do you think you could be 90% confident that the 2.43 second mean is within 0.01 second of the actual mean?
Do you think you could be 90% confident that the 2.43 second mean is within 0.03 second of the actual mean?
Give your three answers and briefly explain your thinking:
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yes
no As explained above the tie differ by more than .1
no The difference above is till just .03 not near .1
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Question: What, if anything, could you do about the uncertainty due to each of the following? Address each specifically.
· The lack of precision of the TIMER program.
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Try to find a new program to use
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· The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
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Practice at timing could help
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· Actual differences in the time required for the object to travel the same distance.
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If it takes a different time theres not much you could really do
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· Differences in positioning the object prior to release.
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Keep track of the previous location with a mark on the ramp
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· Human uncertainty in observing exactly when the object reached the end of the incline.
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Practice again
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Question: 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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Your solution:
Divide the distance tavelled by the time
That gives average speed
confidence rating #$&*: 3
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Question: If an object travels 40 centimeters down an incline in 5 seconds then what is its average velocity on the incline? Explain how your answer is connected to your experience.
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Your solution:
8 cm per second
Average velocity is change in displacement over the change in time
hence 40/5 = 8
confidence rating #$&*: 2
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Question: 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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Your solution:
6.666 velocity
and
10 velocity
confidence rating #$&*: 2
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Question: `qAccording to the results of your introductory pendulum experiment, do you think doubling the length of the pendulum will result in half the frequency (frequency can be thought of as the number of cycles per minute), more than half or less than half?
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Your solution:
Decreases
The longer the sting the longer it takes to go from side to side though gravity may affect it more
confidence rating #$&*: 2
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Question: `qNote 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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Your solution:
Well it depends on the graph no real statistics were given but for a tyoical time based graph
vs movement if starting from time zero there must be a pooint at which time y is zero and
speed x is zero
confidence rating #$&*: 3
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Question: `qOn 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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Your solution:
Well length would have to be at its zero point If length was at zero then I don't know I don't think it can cross the y axis
As the length increases the frequency decreases
&#Good responses. Let me know if you have questions. &#