Zinc Potterman wrote:
Help with 2nd derivative in physics problem please.
I am trying to follow a derivation and am stuck with this step.
If p=r/a, then du/dr = (1/a).du/dp (which i think I'm OK with)
and d2u/dr2 = (1/a)^2.d2u/dp2 (which I'm not)
Why not?
d^2u/dr^2 = d/dr (du/dr)
= 1/a d/dr (du/dp)
= 1/a dp/dr d/dp (du/dp)
= 1/a 1/a d^2u/dp^2
= (1/a)^2 d^2u/dp^2
Where is the problem?
(2's are powers here of course)
Commonly denoted on usenet with an "^".
I'm not sure if it is relevant but earlier on in the text a substiitutuion
is used u = r.psi(r) where psi is a function of r
No, not relevant.
Apparently you are studying the Schroedinger equation
for spherically symmetric systems?
Bye,
Bjoern
.
