course Phy 232
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?
I think little but definitely not all of the discrepancies are explained by the lack of precision of the timer. There is some other error mainly contributing to the different times of the trials.
• 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?
This is probably the biggest factor involved in the error. Human error is greater than the timer error. It is hard to actually click the mouse the exact same time. There is some delay in reflexes.
• 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?
This is not a big contribution to the error of the data. The slope of the ramp is the same, as well as gravity is a universal constant. The time for the object to travel the same distance should be identical.
• Differences in positioning the object prior to release. To what extent to you think the discrepancies are explained by this factor?
Positioning the object prior to release would be a great error. The ball should be at the exact same starting position for each trial in order to get identical 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?
This is a big contribution to error. What constitutes when the ball reaches the end of the incline? Is it when the ball just hits the end, or should all of the ball pass the incline? Whichever method is chosen should be the same method for all of the trials.
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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?
The timer would not contribute greatly to uncertainty.
• 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?
This would contribute to uncertainty slightly.
• Actual differences in the time required for the object to travel the same distance.
This would not contribute to uncertainty.
To what extent to you think this factor would contribute to the uncertainty?
• Differences in positioning the object prior to release.
To what extent to you think this factor would contribute to the uncertainty?
This could slightly impact the uncertainty.
• 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?
This would greatly contribute to uncertainty.
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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.
What do you think you could do about the uncertainty due to this factor?
There is not much that can be done about this uncertainty. The timer program is pretty accurate and not many programs can be more accurate.
• The uncertain precision of human triggering (uncertainty associated with an actual human finger on a computer mouse)
This uncertainty can be controlled by automating the trigger. Perhaps a sensor can be set that will automatically sense when the ball is rolling down the hill. This means that there would be no need for a human trigger.
What do you think you could do about the uncertainty due to this factor?
• 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?
There is not much that can be down for this uncertainty.
• Differences in positioning the object prior to release.
What do you think you could do about the uncertainty due to this factor?
You can mark on the ramp exactly where the ball should be positioned for each trial. Therefore, the ball can be put in the exact same position for each trial.
• 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?
This method can be automated. A computer sensor can be placed at the end and when the ball passes the sensor is when the time can be recorded.
Good work.
You appear to be copying and pasting your access code, as I requested. However it appears that you might be copying it from an HTML editor, or perhaps a word processor set to HTML, rather than a text editor, and the numbers are not being represented correctly. Can you change the file you are using to a pure-text file?
Thanks.