Move mouse into the applet region, do a mouse click and hit h-key to toggle hide/show toolbar function.
You can type up to three different x(t), y(t) functions
Press the SPACE BAR to toggle play/pause mode.
When the animation is in pause mode, press LEFT or RIGHT arrow key will move the time forward/backward 1/20 s.
Press r-key to reset the applet. The following is a FLASH animation show you how to use this applet.

Virtual Physics laboratory Original URL

Fu-Kwun Hwang, Dept. Of Physics, National Taiwan Normal University.