# Boundary conditions

• May 12th 2010, 05:55 AM
calypso
Boundary conditions
if we use the boundary condition at r=0, a = 0, for the following equation

a = C1r + C2/r + qr

is it safe to say that C2=0? and thus:

a = C1r + qr
• May 12th 2010, 06:16 AM
Jester
Quote:

Originally Posted by calypso
if we use the boundary condition at r=0, a = 0, for the following equation

a = C1r + C2/r + qr

is it safe to say that C2=0? and thus:

a = C1r + qr

Yes, otherwise $a$ becomes unbounded.
• May 12th 2010, 06:25 AM
calypso
what do you mean by unbounded sorry?

If you sub in a = 0 and r = 0, you are left with

0 = C2/0

however this make no sence because dividing by 0 should give infinity
• May 12th 2010, 06:32 AM
Jester
Quote:

Originally Posted by calypso
what do you mean by unbounded sorry?

If you sub in a = 0 and r = 0, you are left with

0 = C2/0

however this make no sence because dividing by 0 should give infinity

If you fix $c_2$ then as $r \to 0$, then $a$ grows without bound ( $a \to \infty$).
• May 12th 2010, 07:41 AM
calypso