Researcher needs formula(s) for field problem

Hello I am a Sasquatch researcher in the Pacific North West. We have a curious habit of the species, for whatever reason, they break trees of varying sizes. This is not new to the field but this is where my engineering background comes in and my mathematical mind want to know two things. What is the force needed to break the tree at a certain point, and at what point on the tree would the force need to be applied.

I took courses in “physics, strength of materials and mechanics” and know there is formula(s) to get the answers I am looking for. I have just been out of any of this for so long that I cannot come up the solutions that would greatly benefit this field of research.

I know to get answers the tree will have to be treated as a conical frustum type beam, fixed at one point, and for the material it will have to be green pine. What I am looking for is a formula(s) to do in the field calculations when the researcher has the variable of the of tree’s shear strength.

All dimensions are in inches and I need answers in inches and Ft/Lbs, below is the draft for visual help.

http://i79.photobucket.com/albums/j135/TooRisky/Treebreakcalculation_Layout1.jpg

Thank you for your time and efforts, please E-mail me if there are any questions

Steve (toorisky4u@gmail.net)