Spring system in the form of a fishing rod

[vandelay]

I am looking to describe the flex/bend of a fishing rod with the handle level and a weight attached to the tip. Well, my quest is a bit bigger but this is the essence of the problem. Can anyone help me develop a differential equation for this system? I'm completely blank on this one..

Kjetil

 

[Colbhaidh]

Might not understand th question correctly but doesnot require differential equation.
Assuming the rod has a length L and a modulus of elasticity E, with weight W at one end, the other end assumed rigid:

Deflection = WL^3/(3EI)

Defelection at point X on rod <L = WX^2(3L-X)/6EI (X=0 at support)

where I is the moment of inertia of the rod.

Stress at a specific point x = Wd(L-X)/I where d is the distance to the neutral plane.