Last Updated: 7/5/07
Excel/VBA Spreadsheet for Projectile Motion
If you click on the title below, a
Microsoft Excel workbook will be downloaded to your computer. This workbook
uses a module written in Visual Basic for Applications (VBA), Excel's macro
language. It was written under Windows, but should work under MS Office running
on a Macintosh. Earlier versions of MS Office on both platforms may not support
all features used in this workbook.
Disclaimer
No warranties, expressed or
implied, are made that this program is free from error, or is consistent with
any particular standard of merchantability, or will meet your requirements for
any particular application. This program should not be relied on for solving
problems whose incorrect solution could result in injury or lost property. If
you use this program in such a manner, it is at own risk. The author disclaims
all liability for direct or consequential damages resulting from your use of
this program, i.e., SOFTWARE THAT IS FREE HAS NO GUARANTEE!
This Excel workbook contains a
macro written in Visual Basic for Applications, so that when you open it you
will probably see a warning like, "[filename] contains macros. Macros may
contain viruses. It is always safe to disable macros, but if the macros are
legitimate, you might lose some functionality." Then you are given the
choices: "Disable Macros", "Enable Macros" and "More
Info". In the case of this spreadsheet, you must select "Enable
Macros" or it will not work at all! (If you not even offered this choice,
then your security is probably set at "High." You must have your
security level in Excel set at "Medium," which allows you to
"choose whether or not to run potentially unsafe macros.") My virus
checker is set to update automatically every day (yours should be too!). You
might scan these materials (and anything else containing macros you might
download from the Internet) before opening them, but then you MUST enable
macros!
Projectile Motion (Updated 7/5/07)
This workbook computes the
trajectory of a spherical projectile with fluid drag included. It also
demonstrates some additional things that one can do with the Excel/VBA
combination. It is actually clearing the screen and replotting at every
timestep, but on a fast computer you won't even notice the refresh. For certain
combinations of input parameters (e.g., a very light projectile launched in a
very heavy fluid - like a beach ball let go from under water) the calculation
will go unstable unless you reduce the timestep below the default value.
Eventually we will implement an automatic timestep control in the Runge-Kutta
procedure used to integrate
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