Experimental Measurements

We try to get across three concepts in this lab that will be useful in everything we do in lab this
semester:  quote numbers to the proper number of significant figures (not just whatever the
calculator displays); express numbers and perform calculations using scientific notation; and 
estimate experimental error.

The exercise is pretty self-explanatory.  The final section requires that you build a simple
pendulum.  I would look for a length of string and a small weight (fish sinkers work well).  Need
a timer?  Here is the link to a very small program that creates an on-screen stopwatch -
http://www.download.com/3001-2350_4-10332723.html.  It is shareware with a evaluation
verson, but it should work great for this exercise and then you can delete it.

Here are a few notes on doing calculations that I have used over the years.  When performing
chain arithmetic like the calculation of the acceleration due to gravity in the last part of this lab,
do you write down intermediate results only to re-enter them into your calculator?  You not only
lose time but accuracy in doing this.  Any calculator keeps what are called "guard digits."
These are extra digits at the end of the number that are not displayed.  The purpose is to guard
against round-off error, the very thing that you introduce when you write down intermediate
results.  Keep the intermediate results in the calculator, if you can, and your answer is more
accurate.

The final part of this exercise (as well as several other labs in this course) require the use of the
number pi (3.1415926...).  Any calculator worth its salt has this number stored already.  Look
for it and use the stored version.  It will be more accurate.

Speaking of calculators, look yours over and determine how to enter numbers in scientific
notation.  Quite often in astronomy, we need numbers very large or very small and standard
notation just doesn't work very well.  Don't have a scientific calculator?  Yes you do, if you run
WINDOWS.  Look under Start/All Programs/Accessories and find the program named
Calculator.  The default is to display a standard calculator (only four functions  + - X /).  Go to
the view tab and change the display to scientific.  Now you have a full function scientific
calculator.  Experiment with it until you learn how to use scientific notation.