So glad you found it helpful Kris :)

its almost like you can take the moment at D to find Ax in terms of P but you cannot take the moment at A to find Dx in terms of P. This is very strange...

I’ll take a guess at what you did and explain why it wouldn’t work 😊 Referencing the steps by the equation numbers I used in the problems: Remember, for the system there are only 3 unique equilibrium equations - forces in X and Y, and the sum of the moments about any point are zero. 3) You found GLOBAL moment about A, getting Dx in terms of P. 6) You cut the system between points C and D, then took the moment about D to get an equation with Ax and P. BUT - this is actually the same as the GLOBAL equilibrium about point D. We’ve already used global equilibrium in 3), so this does not give you a unique equation and cannot be used for your solution. If you wanted to start with the global moment about A, you could use the method of joints until you were able to solve for P. You would get the right answer, it’s just a bit more labour intensive. By starting at D and cutting between B and C, we get a unique moment equation for that part of the system which helps save some time. Both strategies are correct though! Hope that explains it and thanks for watching!

@@learnwithpi ok so we cant solve global equilibrium more than once (using two different points as a reference) and try to combine both equations for an answer. I think that's what you're saying? So we need to stick with one equation for GLOBAL equilibrium and for the other equations we need to cut portions of the system in half?

Yes, only one equation for the global equilibrium of the entire system :) Other equations can come from other cuts or by using the method of joints. If you wanted to review these I bet there's a truss section in your textbook with lots of practice. They're the same tools that apply to cables in this case :) Good luck!

@@learnwithpi I think I got it. Time to practice practice practice! Your videos are more helpful than the textbook. Thanks again!