1. The problem statement, all variables and given/known data Stress tensor at a point Q in a body has components: pij: | 1 -1 0 | |-1 2 1 | | 0 1 3 | (i) Calculate components of the stress force f across a small area of surface at Q normal to n = (2,1,-1). (ii) The component of f in the direction of n is called the normal stress while the component of f tangential to the surface is called the shear stress. Find the normal stress and the shear stress at Q. 2. Relevant equations f = fi = pijnj 3. The attempt at a solution (i) I take the stress force at Q across the surface normal to n to be the product of the stress tensor pij and the normal vector n and arrive at: f = (1x2 + -1x1 + 0x-1)i + (-1x2 + 2x1 + 1x-1)j + (0x2 + 1x1 +3x-1)k = ( 1, -1, -2 ) (ii) I think this is a simple algebraic exercise - ie what components of ( 1, -1, -2) project onto n to give the normal stress, and which components project onto the plane normal to n to give the shear stress. Am I reading this correctly, and what is the most efficient way of computing these components? I can't help but think the answer might be staring at me from within the tensor pij.