1. The problem statement, all variables and given/known data Hi guys, i came across a paper about an Investigation of pencil-lead breaks as acoustic Emission sources by Markus G.R. Sause (it's downloadable everywhere). The Setup of the Experiment can be seen in the Picture i attached. Now the Problem i have is to find the correct formula on how to find the breaking force of lead, where the elastic modulus and density are defined. E=10.5 Gpa, ρ=1.78 Mg/m3. In the table below, the calculated forces are listed in the table "Force (experimental)". My attempt is to use the formula of Modulus of rupture, E = M.y/I and get the value for Bending Moment. For the sake of example, i am using 0.5 mm Diameter, 60° angle, 4 mm lead length. Assuming that i am using the correct formula, i calculated the Bending Moment on the System. This is where i stuck since im not sure what are all Forces acted on the lead. (Please see my attempt in the attachment). 2. Relevant equations Once all Forces are known, use force Equilibrium where Fx=0, Fy=0, M=0. 3. The attempt at a solution Please see the Images i attached. Thanks! I appreciate your help!