... Dimensional Analysis (9.28.10)

Today, we learned about Dimensional Analysis. It is compared to converting between different currencies but with different units. There are 4 steps to Dimensional Analysis.

1. Find a unit equality
2. Find the conversion factors
3. Apply the conversion factor
4. Cancel Units

For example, we want to know how many seconds there are in 5.2 hours.

So that was today's lesson. Short and sweet, but very important. Study hard!

...Scientific Notation and Significant Digits (9/23/10) / Monday, September 27, 2010 @4:14pm

Today, we learned about Significant Digits. These digits are numbers that must be recognized in order for you to have the most accurate results in a measurement. However not all numbers are significant, the rules for significant numbers are listed below.
-Non- zero units are always significant.
-If the zero is a place keeper it is "generally" not significant.
*such as in 0.001 there is only one significant number (1) however in a case such as 0.100 there are three significant    numbers (1,0,0)
-any numbers to to the right of a decimal point are significant if they come after a non-zero number

When adding or subtracting round to the least precise number (this also applies to division and multiplication)
example: 7.4212-3.54=3.88 (since the least precise number is 3.54 having only three significant numbers the original answer being 3.8812 is brought down to 3.88) 


We also had a refresher on scientific notation. scientific notation is used for expressing very large numbers in the form of a smaller looking equation. We can also use them to express very large significant digits.
 

 

... the SI System and Percent Error (9.21.10)

Today, we learned about the Different Prefixes that are used with SI Units. Prefixes are used to show a decimal multiple or a fraction of the unit. The SI System also uses many prefixes to represent very big and very small numbers. The SI system has 20 prefixes, but the ones stated in the chart below are the ones that we will use throughout the year. 

*Note: one prefix that was left out is fento (fm), which has a standard form of 10 to the power of -15 (10^-15)

We also covered Experiment Accuracy. The maximum accuracy of any measurement is one half (1/2) of the smallest division of the measuring device. For example, a ruler with measurements of millimeters (mm) has a maximum accuracy of ±0.5mm (plus or minus 0.5 millimeters). 

The last topic we covered this class is about Expressing Error. Error is a fundamental part of science. No matter how hard we try, we cannot escape error. And there are usually 3 reasons for error: 1) Physical Errors in a measuring device, 2) "Sloppy" measuring, 3) Changing ambient conditions. Now, there are 2 different possibilities for calculating error, Absolute Error and Percent Error

The way we calculate Absolute Error is the measure value minus the accepted value. This is the method that we will sometimes use.

*AbsoluteError = Measured - Accepted

With Percent Error on the other hand, we get the measured value minus the accepted value divided by the accepted value multiplied by one hundred. Confusing? Look below. 

Until next class my friends, live long, prosper, and do your blog because it counts for 20% of your grade :)

-Michael&Jerome