I have a second order differential equation, in terms of a term that was previously obtained from numerically solving another equation.
Numerical solution of equation before 2nd order equation:
Rgas = Rationalize[8.314]; (* gas constant *) acoef[tc_, pc_] := (27*Rgas^2*tc^2)/(64*pc); bcoef[tc_, pc_] := (Rgas*tc)/(8*pc); Clear[p, t]; latentK = 76.9*10^3*39*1.67*10^-27*6.022*10^23; tcK = 2223; (* Kelvin *) pcK = 16*10^6; (*Pa *) eqn = (p - Rgas*t)*v^3 - bcoef[tcK, pcK]*p*v^2 + acoef[tcK, pcK]*v - acoef[tcK, pcK]*bcoef[tcK, pcK]; asolns = Solve[eqn == 0, v] ; (eqn /. asolns)[] ; realroot = v /. asolns[];
And now, my 2nd order differential equation, in terms of
realroot, which is a function of p(t) an t:
NDSolve[p''[t] == latentK/(t*realroot), p[t], t]
But this is not working.
I guess one of the problems is that
realroot is not defined to be a function of p(t) and t...