We will use a computer utility called Microsoft Excel to keep all of our numbers and do our calculations for us. First, we will do the calculations ourselves to learn what we are doing. Then we will configure Excel to do the work. We start by loading Excel with our constants and our initial conditions.

Notice that the values are in column B and the units are in column C.

Each cell has a first and last name. The first name is the letter at the top of each column.
The last name is the number of the row that contains that cell. The cell that
contains our first number is: **B3**. Its value is 101300.00. Find that cell now
and be sure you understand the naming convention.
When we mention a cell, we must be polite and always use its full name.

With a few exceptions, Excel has been configured to show all numbers with two decimal places. That keeps the numbers all lined up and easy to read. As you can see, cell B6 is an exception. It is a small number and without the exception it would show the value 0.00. That would be confusing as we look at all the values.

Excel cannot process the units of measure. Remember that I was careful to point out how we must always keep track of our units of measure and include them in our arithmetic. We will have to give Excel just the numbers while we keep track of our units. When needed we can put more comments in the worksheet.

This will not be a tutorial on Excel, but some things should be described.
You can do a Google search on **tutorial Excel** to learn more about Excel.

Look in the Excel sheet, and find cell B16. It has the pressure from the bicycle pump, in psi. We are using scientific notation for our calculations so psi is converted to Pa. When you have the Excel sheet on your computer you can click on cell B17 and you will be able to find this:

Put in words, that means start with the rocket gross volume (already put in cell B10) and subtract the water volume (already in cell B12). All the cubic centimeters not filled by water are filled by air. Look at all the cells already shown and see if you understand these two sentences.

For cell B24 I have calculated the mass of the air unpressurized. B25 has the mass after the rocket is pressurized. Look back up in B19 to see the pressure in newtons per centimeter squared.

All the remaining cells are calculated by the worksheet. We will not be changing them by hand. We hired Excel to do those calculations.

Pay close attention to information contains in this worksheet. The Worksheet is named
**Initial Conditions 01**
When we build another rocket or launch with different conditions, we will copy this
worksheet to **Initial Conditions 02**. By creating a new worksheet for each launch
we can can re-visit our previous launches. If you have Microsoft Excel, or
any worksheet program, you can enter the data shown here. There is
a copy of this workbook on the web page here:

Excel Workbook 01

If you do not have Excel, write all this information on a sheet of paper. Use the
format I have provided and put all your numbers and descriptions in the same
columns shown here. You might print it out, but your best advantage is served by
writing this down yourself. Doing that will help you remember all the things
we discuss.

Now its time to continue on and discuss the thrust.

Dec 2014

Bryan Kelly

send comments to: on line at bkelly dot ws