Problem to resolve ODE of a Circular Membrane of Science of Construction

[giovanniferdina]

Hi I’m Giovanni and I 'm a new user.I want to ask you why when i try to resolve my ODE of circular membrane in circular coordinate placed
in a centre of circular membrane:

DSolve[{w''[r] + (1/r) w'[r] + p == 0, w[R] == 0, w'[0] == 0}, w[r], r] 

r=indipendent variable ,w = spostament membrane ,p=uniform pression R= radius of circular membrane
and I impone my boundary condition ,

in Mathematica 10 as out ,appears to me an error :

"DSolve::deqn: Equation or list of equations expected instead of True in the first argument {p+w'[r]/r+w''[r]==0,w[R]==0,True}. "

What I’m wrong??? I try the error but i don’t understand the error…I hope I was clear.
In the image is the first line.

[mthiel (Marco Thiel)]

Hi,

I might be misunderstanding your problem, but if you use w[r] instead of w, it appears that you get the expected result.

 v = DSolve[{\!\(\*SubscriptBox[\(\[PartialD]\), \(r, r\)]\(w[r]\)\) + 1/r \!\(\*SubscriptBox[\(\[PartialD]\), \(r\)]\(w[r]\)\) + p == 0, w[R] == 0, 
   w'[0] == 0}, w[r], r]

You get

and no error message. You might want to execute

ClearAll["Global`*"]

first.

Cheers,

Marco

[giovanniferdina]

Thanks Marco!!!
I solved the error with your command.Thanks again.