MyPhysicsLab – FAQ – Frequently Asked Questions

Software Problems

Q: How can I show the simulations to my class?
A: You can copy parts of the website onto your local computer hard disk. See the sections below on Displaying Simulations Off-line and Changing Size of Display.

Q: Why don't the simulations play in my browser?
A: Make sure that you have Java turned on in your browser. For Internet Explorer on Windows go to "Internet Options", click the Security Tab, and make sure that "Java permissions" are enabled (ie. set to anything other than "disable"). You also should enable "scripting of Java applets".

Q: Why is the animation jerky?
A: Some browser & platform combinations don't give enough time to the applet to allow for smooth animation. One thing to check is whether you have a Java compiler enabled in the preferences for your browser. For Internet Explorer on Windows this is in Internet Options, under the Advanced tab, called the "JIT compiler".

Q: Clicking the buttons doesn't do anything.
A: For the buttons outside the Java applet, this is a known problem on Macintosh Internet Explorer (its a fault with Internet Explorer). But you can try making sure that "scripting of Java applets" is enabled in your browser security preferences.
For the buttons inside the Java applet, if you experience this please report as much information as you can about it to me at

Q: The math symbols don't look correct.
A: I am using HTML 4.0 unicode characters for some greek characters and math symbols. There is some good information and test documents at Alan Wood's Unicode Site. You might find information on how to get your browser to understand unicode there.

Free Source Code

The Java source code for the MyPhysicsLab applet is available at You should be able to download individual files there by right-clicking on a file. You can also try accessing that directory by anonymous ftp at   NOTE: if you get the message "page cannot be displayed" after clicking the ftp link, hit the "refresh" button in your browser and it should work. Or try typing the ftp address directly into your browser.

The source code is covered by the GNU General Public License. Using the GNU GPL ensures that all subsequent improved versions will be free software. Here free means freedom rather than "no cost".

I would like to hear from anyone downloading, using, or improving the source code. Send me a note at about what your interests are with the code. I would also appreciate if you could provide a link to if you use the source code on your website or at your school.

Simplified Source Code

A simplified text-only version of the source code suitable for students to experiment with is shown here.

Displaying Simulations Off-line

If you are giving a lecture and using a computer to display a simulation, you are typically not connected to the internet. You can download a copy of this website onto your computer for display off-line. It is accessible via anonymous ftp. Here steps to take:

  1. If you are using Internet Explorer, type into the address of the web browser (note: I am unable to ftp from Netscape Navigator).  The directory of files that make up the website should display.
  2. Copy the files Lab.jar (contains the Java applet) and stylesheet1.css (used by all the .html files)
  3. Copy whichever of the .html files you want.
  4. Copy the /images/ subdirectory if desired. The images are not used by the Java applet, they are only needed for images appearing in .html files.
  5. To use the files now on your local hard disk:   in Internet Explorer, click the file menu, choose "open" and then click the "browse" button. Locate the desired .html file on your hard disk, and open it.
  6. Try disconnecting from the internet to be sure that it is all working.
Tips on using ftp within Internet Explorer:

Changing Size of Display

If you need a larger display to fill the screen for a presentation, you should follow the instructions above to get a copy onto your local hard disk. Then use a text editor to modify the .html file that shows the simulation of interest. The line to modify will be near the beginning and look something like this:

   <applet code = "Lab.class" name="Lab" archive="Lab.jar"
   codebase="." width=500 height=300>

You can change the width and height to whatever you need. Then save the file and open it with your browser as described above.