#$&*
course phy 242
6/7/2013 around 1:30 pm
Most queries in this course will ask you questions about class notes, readings, text problems and experiments. Since the first two assignments have been lab-related, the first two queries are related to the thoseexercises. While the remaining queries in this course are in question-answer format, the first two will be in the form of open-ended questions. Interpret these questions and answer them as best you can.
Different first-semester courses address the issues of experimental precision, experimental error, reporting of results and analysis in different ways and at different levels. One purpose of these initial lab exercises is to familiarize your instructor with your work and you with the instructor 's expectations.
Comment on your experience with the three lab exercises you encountered in this assignment or in recent assignments.
*********************************************
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 to what extent do you think the discrepancies could be explained by each of the following:
The lack of precision of the TIMER program.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The lack of precision of the computer time would be to that of 0.01 accuracy. Although the timer does not maintain the same tenth value digit, it does maintain precision level in which the numbers are close to each other through 0.1 accuracy. The discrepancies of the times not being 0.01 accuracy demonstrates that either the person was not accurate in pressing time or either the timer was not held to 0.001 places.
#$&*
The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
As explained previously, human clicks on the computer, the discrepancies of the times varying by 0.1 place is well explained. It is more acceptable for the timer to be less precise since human clicks are not constant and accurate every time.
#$&*
Actual differences in the time required for the object to travel the same distance.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
When taken into the same distance travelled by the steel ball, the times should be the same, if the not the same the values of the time for each trial should be 0.001 close to each other. From the data gained it can be explained that when experimented with the steel ball, either the person allowed the ball to travel farther than the 50 cm length or less to gain such results that have 0.1 accuracy.
#$&*
Differences in positioning the object prior to release.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The position of the release also affects the 0.1 difference in the times. If the ball is placed past the releasing point or a little before the releasing point, the time will be 0.1 off, which is demonstrated by the data.
#$&*
Human uncertainty in observing exactly when the object reached the end of the incline.
To what extent to you think the discrepancies are explained by this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Human observation of the end of the incline can be shaky as in one can be uncertain on when the ball crosses the 50 cm point. As human cannot look at the ball from different point so f view, so when watching it from one point of view, the ball could have already past the 50 cm when the human calls time or it could still have 0.01 time left till it hits the 50 cm line.
#$&*
*********************************************
Question: How much uncertainty do you think each of the following would actually contribute to the uncertainty in timing a number of trials for the ball-down-an-incline lab?
The lack of precision of the TIMER program.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The uncertainty of the computer timer would be +-0.01.
#$&*
The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The uncertainty of the human clicks could contribute +-0.01.
#$&*
Actual differences in the time required for the object to travel the same distance.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The uncertainty of the length of the inline traveled referred to time would be +-0.001.
#$&*
Differences in positioning the object prior to release.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The uncertainty of the release position referred to time would be +-0.001.
#$&*
Human uncertainty in observing exactly when the object reached the end of the incline.
To what extent to you think this factor would contribute to the uncertainty?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The uncertainty of human observation referring to time would be +-0.01.
#$&*
*********************************************
Question: What, if anything, could you do about the uncertainty due to each of the following? Address each specifically.
The lack of precision of the TIMER program.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Nothing can be altered about the precision of the Timer program, as long as the other factors are kept precise the timer will show more precise results.
#$&*
The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
The one thing that can be altered from the human clicks is setting an electronic clicker that will click the mouse when the ball hits the 50 cm line therefore triggering the click. Other than that, it cannot be altered, only that, keep the same person clicking the mouse so that the clicks are constant.
#$&*
Actual differences in the time required for the object to travel the same distance.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Find the difference in time it took for the ball to slide down the incline and observe the ball on the second time to see if it matches the time difference you attained the first time, this will allow the time and data to be more accurate.
#$&*
Differences in positioning the object prior to release.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
Setting an immovable trigger in front of the ball which only moves when releasing the ball, will allow the releasing point to be constant for all the trials.
#$&*
Human uncertainty in observing exactly when the object reached the end of the incline.
What do you think you could do about the uncertainty due to this factor?
your answer: vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
By positioning ones self at the same vertical point of view each time when observing the ball will allow more constant results as well as non-altering timing of the ball crossing the 50 cm line.
#$&*
"
&#Very good work. Let me know if you have questions. &#