Question

I need help to sum of torques.

Answer 1

Is there somebody wby that big equation?the sum of torques is given by that big equation?

Answer 2

Yes, it is. You need to identify all of the forces at work in the equation, and the calculate the torque via
\[ |\tau| = F\cdot x\cdot \sin(\theta)\]
where x is the distance from the point in question to the spot where the force acts and theta is the angle between the direction of the force and the direction of the vector pointing from your point to the spot where the force acts. It's a rather complicated example if you have no idea how to calculate torques, so might I suggest practicing on a simpler problem? See the following website (which actually describes a problem that is almost exactly identical to yours, just upside down....) http://physics.bu.edu/~duffy/py105/Equilibrium.html

Answer 3

Thank you, Jemurray3. I will look at this example you just sent to me. If there is something I will ask again, after I have read it. Thank again :-)