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Phy 121
Your 'question form' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
** Question Form_labelMessages **
Text related Question from A2
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2. What is the uncertainty in the following reported measurements, and what is the percent uncertainty in each?
• 5.8 centimeters
• 2350 kilometers
• 350. seconds
• 3.14
• 3.1416
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I am still a tad confused, do I always assume it is 0.05 when it is a decimal and that it is either +/- 5 when it is not a decimal?
2350 kilometers: +/- 5 km
2350+ 5= 2355 2350-5= 2345
(5/2350) * 100= 0.2%
350. seconds: +/- 0.05 seconds
350. +0.05=349.95 350.-0.05=350.05
(0.05/350.)*100= 0.01%
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350. seconds is accurate to the second, to the uncertainty could be +- 0.5 seconds, not +-0.05 seconds.
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3.14 seconds: +/- 0.01
3.14+0.01= 3.15 3.14-0.01= 3.13
(0.01/3.14) * 100=0.3%
3.1416 seconds: +/-0.00001
3.1416 + 0.00001= 3.14161 3.1416-0.00001=3.14159
(0.00001/3.1416) * 100=0.0003%
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As I indicated previously, there are two possible ways to assess the uncertainty, and each corresponds to a different interpretation of the measuring process.
For your first two answer you interpreted the uncertainty one way, assuming the number to be accurate to the given number of significant figures so that the uncertainty was half a 'division'.
For your second two you assumed an uncertainty equal to the full division.
The situation determines which is more appropriate.
However you book will probably want you to go with the latter interpretation.
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