- #1

salamikorv

- 36

- 2

- Homework Statement
- What decides Tau_V sign?

- Relevant Equations
- Tau_T-Tau_V

Im so confused on these solutions here for the shear stresses. Why is Tau_V sometimes negative and sometimes positive? Can someone please explain this and maybe illustrate?

Here for example.

Heres the solution for problem b):

Here Tau_V (talking about F_xQ/(Ir) ) is negative, so how im thinking why it is negative is because the moment is making so that the shear force on point P is directed to the negative x-direction, but on the drawing its directed to the positive x-direction??

And for point Q, Tau_V is positive? Why is it not negative? I thought since the bending onto the cross section is going clockwise, making the shear force at Q go at positive z-direction, it should be positive? But its wrong and how should i think about this?

Here for example.

Heres the solution for problem b):

Here Tau_V (talking about F_xQ/(Ir) ) is negative, so how im thinking why it is negative is because the moment is making so that the shear force on point P is directed to the negative x-direction, but on the drawing its directed to the positive x-direction??

And for point Q, Tau_V is positive? Why is it not negative? I thought since the bending onto the cross section is going clockwise, making the shear force at Q go at positive z-direction, it should be positive? But its wrong and how should i think about this?