## How to apply the boundary condition as DERIVATIVE in FlexPDE

General discussions about how to formulate a script for FlexPDE.

### How to apply the boundary condition as DERIVATIVE in FlexPDE

Dear All

I want to solve the following ordinary differential equation related to deflection of the cantilever beam.
dxx(w)=-P*x/E/I
BC1: w=0 at x=0
BC2: dw/dx=0 at x=0
I cannot impose the boundary condition BC2 correctly.
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TITLE 'Cantilever Beam' { the problem identification }
COORDINATES cartesian1 { coordinate system, 1D,2D,3D, etc }
VARIABLES
W
H

DEFINITIONS

L=1
P=200
E=70e9
I=1/12*0.03^4
ans_analytical=-(1/6)*P*x^3/(E*i)

EQUATIONS { PDE's, one for each variable }
H: H=dx(w)
W: dx(H)=-P*x/E/I

BOUNDARIES { The domain definition }
REGION 'domain' { For each material region }
START(0) { Walk the domain boundary }
point value (w)=0
point value (H)=0
LINE TO (L)

MONITORS { show progress }
PLOTS { save result displays }
elevation (w,ans_analytical) from (0) to (L) as "deflection"
END
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Why my script is not resulted in the correct solution?
How can I apply “Natural (Or load) Boundary condition” to solve my problem?
How can I impose boundary condition as DERIVATIVE in FlexPDE?