Shear Stress
Transverse shear forces cause shear stress on a beam's crosssection at height y = y_{1}:
 Shear stress is zero at the top and bottom surfaces.
 y = yvalue of "cut", y = y_{1} (where we are finding the stress).
 V = shear force on the crosssection.
 A^{*} = area on the opposite side of the "cut" from the neutral axis; i.e., area above y_{1}.
 y^{*} = distance from neutral axis to the centroid of A^{*}, NOT the distance to the cut.
 I = moment of inertia of the entire crosssection.
 t = width of beam at y (width of cut).
 Q is the first moment of area of A^{*} with respect to the neutral axis; Q = A^{*}y^{*}.
 q is the shear flow; q = t t .

