Re: Help with solving ODE

*To*: mathgroup at smc.vnet.net*Subject*: [mg81789] Re: Help with solving ODE*From*: Norbert Marxer <marxer at mec.li>*Date*: Wed, 3 Oct 2007 06:10:59 -0400 (EDT)*References*: <fdvdq7$sul$1@smc.vnet.net>

On 3 Okt., 08:45, Pioneer1 <1pione... at gmail.com> wrote: > Hi, > > Can anyone help solve this linearized differential equation: > > Iy'' + ky' = 2GMmd/a^2 > > Primes are time derivates of y (=theta=excursion angle). Is it > possible to solve this for the initial conditions y(0)=0 and y'(0)=0? > > I got the solution at sci.math for the non-linear version and I want > to compare the two. Here's the link to sci.math thread: > > http://groups.google.com/group/sci.math/browse_thread/thread/a6ee2f78... > > Further information is also available at sci.physics.research > > http://groups.google.com/group/sci.physics.research/browse_thread/thr... > > Parameters are: > > > y = theta = excursion angle in radians > > A = I = moment of inertia = 13,138,117.34 g cm^2 > > B = R = damping = for now I assume this to be zero > > C = k = torsion constant = 724.68 g cm^2 sec^-2 > > d = moment arm = 93.09 cm > > D = 2GMmd = 2 * 6.67*10^-8 * 158100 * 729.8 * 93.09 = 1432.82 > > a = distance between weights = 22.10 cm > > I would truly appreciate help with this. Thanks Hello With your data and units you can use sol=DSolve[{13.138 10^6 y''[t]+724.68 y[t]==1432.82/22.10^2,y'[0]==0,y[0]==0},y[t],t]; Plot[sol[[1,1,2]],{t,0,3000}] I hope this helps. Best Regards Norbert Marxer