The applet on Page 2 simulates the motion of a space probe passing a planet. The final speed of the space probe depends on the planet's speed. The change in the speed of the probe as the probe passes the planet is called "gravitational assist" or "slingshot effect". The applet demonstrates that the effect can be understood in terms of the Galilean transformation of velocity.

Currently, no detailed information about the applet is available from the applet's Help menu.