SI System and Percent Error Summary

SI Prefixes


The SI system uses many prefixes to show very large or very very small amounts of numbers.

Eg.

Tera (T) 10^12
Giga (G) 10^9
Mega (M) 10^6
Kilo (K) 10^3
Hecto (h) 10^2
Deca (da) 10^1
Fundamental Units
Deci (d) 10^-1
Centi (c) 10^-2
Milli (m) 10^-3
Micro (u) 10^-6
Nano (n) 10^-9
Pico (p) 10^-12
Femto (fm) 10^-15

Here's a link where you can learn more about the SI System

http://www.youtube.com/watch?v=ruBZ_yj1mEY

Experimental Accuracy


The maximum accuracy of any measurement  is one half of the smallest division of the measuring instrument.

Eg. Ruler with the lowest of measurements is millimeters. It has a maximum accuracy of +/- 0.5mm

Eg2. The odometer in a car has a maximum accuracy of +/- 50m

Eg3. Graduated cylinder has units of 1.0mL so the accuracy of  a cylinder is around +/-0.5mL

Expressing Error

Finding error is part of science!

There are usually 3 reasons why there is error.

1. Physical errors in the measuring device
2. 'Sloppy' measuring
3. Changing ambient conditions

Calculated Errors


There are two possibilities of calculated errors.

1. Absolute Error
2. Percentage Error

Absolute Error = Measured - Accepted

Positive numbers means you're over the accepted value and negative numbers means you're under the accepted value.

Percent Error


Percent error is the most common out of all the errors.

Percent error can be calculated by

% Error = [Measured - Accepted/Accepted] x 100
(The symbols '[ ]' represent the it's absolute value)

Eg.

[17.5N - 15N/17.5N] x100
= 14%

For more information about Percent Error can be found on this link below :

http://www.youtube.com/watch?v=jm7qUpPyY7w

-Meldrick Mendoza productions. : )