Units of Measurement and Uncertainty in Measurement

Prefixes Used with SI Units

We can put a prefix in front of the unit and change the power of it.

- tera: 10^12                                    - femto: 10^-15

- giga: 10^9                                      - pico: 10^-12

- mega: 10^6                                   - nano: 10^-9

- kilo: 10^3                                     - micro:10^-6

- hecto: 10^2                                   - milli: 10^-3

- deca : 10^1                                   - centi: 10^-2

SI Prefixes

the SI System uses many prefixes to represent very large or very small numbers

Experimental Accuracy 

In general the maximum accuracy of any measurement is one half of the smallest division of the measuring device.A ruler with measurements of the millimeters has a maximum accuracy of positive or negative 0.5mm

Expressing Error 

Error is a fundamental part of science

There are usually 3 reasons for error: 

                     > physical errors in the measuring device 

                     > "sloppy" measurements

                     > changing ambient conditions 

Calculating Errors  

Two different possibilities: Absolute Error, Percentage Error 

Absolute Error

  

Measured value minus accepted value  

Absolute Error = Measured - Accepted 

Percent Error  

Most common 

Percent error = Absolute error/Accepted value 


-Benedict Suratos