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Week Ending August 26 2011

posted Aug 23, 2011, 8:52 PM by Frania Lugo   [ updated Sep 8, 2011, 9:53 PM ]
    This week i learned about Uncertainty of measurements and that when measuring an object it is sometimes not possible to measure the exact value. Also i learned how to measure precision and accuracy the lab consisted of measuring a pipe cleaner with different rulers in order to understand how to measure precision and accuracy. We measured the scale increments of the rulers than measured the pipe cleaner on the different rulers to see what measurements we got. We were given the actual value of the pipe cleaner to see which ruler was more accurate and why. I also learned about the significance of zeros.

   How to know if the ZEROS are significant or not. and what to follow in order to see if they are or not. 
                                 Measurement with an expressed decimal:
Look for the first non-zero digit--it and all digits to its right are significant.
                                Measurements with an understood decimal:
Zeroes that come between the last non-zero digit and the understood decimal place are not significant. To indicate that any of these zeroes should be considered significant you would place a bar over the right-most significant zero.
Examples:
0.00341........3 sig. digs.
1.0040.........5 sig. digs.
0.00005........1 sig. dig.
65000..........2 sig. digs.
40300..........3 sig. digs.
200300.........4 sig. digs. 

                                    Operations with Significant Digits
Any number that represents a numerical count or an exact definition has an unlimited number of sig. digs.
When superfluous digit(s) is/are less than 5, the preceding figure is retained without change. When the digit(s) to be dropped is/are greater than 5, the last place retained is increased by 1. When the digit(s) to be dropped is/are 5 exactly (5, 50, 500, etc), the last retained column is rounded off to be even.
When adding or subtracting numbers, arrange the numbers in columnar form. Retain no column that is to the right of a column containing a doubtful digit.
In multiplication and division, the result should have no more sig. digs. than the factor having the fewest number of sig. digs.
The root or power of a number should have as many sig. digs. as the number itself.


more about zeros >>>> http://www.rpi.edu/dept/phys/Dept2/APPhys1/sigfigs/sigfig/node12.html

Identify the Significant figures in the measurements. 
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