Dear Fu-Kwun,<br />thanks for your comments about the astroblaster. I look at your applet, it is fine, but your consideration is about the collisions, where the speed of the second ball after the collision is not zero. If we would like to arrange the conditions for the highest throw (what is as much as possible done in case of astroblaster), the balls masses must be specific....Based on it would be suitable to create the applet, where coefficient of restitution between the balls are the same, but it can be see, how it works....the key role is the specific mass for the ball, which depends on coefficient of restitution between the balls.<br />I have some videos, it is not problem to create mov files, and by using the videotracker, compare the real astroblaster with model one. Now we are working on creation of the astroblaster from set of four different balls (football, voleyball, ..) and I like to make the videos, measure the real data....<br /><br />Best wishes,<br />Marián