Recent content by crepincdotcom

truthfully I've never heard of laplace transforms, so I'll take your word for it. I've only ever seen the problem addressed as a numerical method wherein each part is solved for some small dt. I wanted to do it with diff EQs if possible. Thanks guys -Jack Carrozzo jack _{at}_ crepinc.com...

I was using the assumption that the mass lost compared to the total mass of the vehicle was negligable in order to make calculations easier, but if I were to include it, it would be some function of the form m(t)=m_{v} - km_{p0}t or the mass of the vehicle plus the initial mass of the...

Thanks, I need to let that sink in for a bit before I can try to apply it. The thrust equation is for the most part a type of step function: x Newtons for 0.5s, y Newtons for 2 sec, and z Newtons for 4 secs. That's a bit hard to express in an equation unless we use peice-wise. Which come...

Hm... I looked that up at http://mathworld.wolfram.com/IntegratingFactor.html Any idea what sort of function I'm looking for to make that integrable? -Jack Carrozzo jack _{at}_ crepinc.com http://www.crepinc.com/

r(v)=(\frac{1}{2}rAc)v^2 or simply r(v)=kv^2 which is not linear, per se. How would I go about this? Thanks, -Jack Carrozzo jack _{at}_ crepinc.com http://www.crepinc.com/

Hey, I've been teaching myself some DEs that I can use for physics and whatnot. I am comfertable with seperable equations, but I can't figure out how to solve this problem. Let's assume we have some rocket with thrust F(t) and drag r(v), plus acceleration due to gravity, g=9.8 m/s/s. Overall...

Oh well... guess I'm not solving that one any time soon. Thanks for the help, -Jack Carrozzo http://www.crepinc.com/

Hey all, I've been working on learning to solve some PDE's. To do this I've been reading other people's tutorials. Here's one on the heat equation: http://www-solar.mcs.st-and.ac.uk/~alan/MT2003/PDE/node21.html This is pretty much the same as the others I've read on the heat equation...

Thanks a lot, both of you. I'm going to spend a few hours pouring over this tonight to attempt to wrap my mind around it, and see what I come up with. For clarification, I'm wondering how we can simply "assume" that if we have an ODE of some form that f(x) takes a particular form. Is it that...

I've spent quite some time since this post's inception working on this... here's where I'm stuck at the moment. By what therom, name, or process does this part take place? I haven't read anywhere about doing this. Is it problam-specific that trig functions happen to work, or a general idea...

Aha... that's smart. But at somepoint won't I still have to use some method to deal with the singularity, because if they orbit but still get closer and closer... eventually some particle is bound to get very close. How do "real" (professional) NBody codes solve this problem? Thanks...

OK... could you explain this tangental velocity concept a little deeper? Thanks, -Jack C http://www.crepinc.com/

No, just x and y. But the issue is not that the distance is evaulated at zero, it's that the distance is CLOSE to zero, giving that large force. The radii idea sounds interesting, but I was going for more of a point-mass simulation. Hmm I'll think about that. Thanks, -Jack C...

I also wrote a tutorial/paper/something on the subject that, let me tell you, is not anywhere close to as good as most of you could likely write. If you'd like to take a look though (suggestions?), you can see it (and the source to my program) at http://www.crepinc.com/projects/nbody Thanks...

http://www.crepinc.com/projects/nbody/nbody.wmv That's the output of my home-made NBody solver. I'm wondering if it looks right to you all. Two things to be aware of: 1) The particles shoot away from the singularity because when they are solved in on timestep with r approching 0, the...