Subject: Re: (no subject) Date: Mon, 03 May 1999 18:44:25 +0200 From: Peter Brichzin <peter.brichzin@brasil.m.shuttle.de> To: Fu-Kwun Hwang <hwang@phy03.phy.ntnu.edu.tw> Hallo Mister Fu-Kwun Hwang, thank you very much for sending all the files. To get a good multimedia lesson is very important for me, because it would be evaluated. A good evaluation will give me a job es teacher. I tried to understand your program. It's not easy because my knowledge in Java is very basic. My problem is now: If I want to change the power of r in aceleration or force F~ a ~ 1/r^2 to F~ a ~ 1/r^x then I have it to change in the method drivs of class movingProjectile. (it works) But this method never is called in whole projectileOrbit.class. And to give a different exponent to acceleration I have to give a argument to method derivs (or are there other possibilities. Is it possible that derivs is callt in rk4. Could you send me please rk4.java or could you help me in an other way with an idea to cahnge it. Sorry that I ask you so much. Probably your time is rare, but it would be a big help for me. Thank you very much Peter Brichzin P.S: To get an imagination whatb I want I send you a modified version: I added a Checkbox to change force. But I can't get the connection between checkbos and method derivs.