The question has asked us to find the velocity and tension in the string whose lenght is L. Let 'r' be the radius of the circular path of the bob. I think the free body diagram looks like this
I want to calculate tension first
In the diagram , T = mg.costheta and mg = T.costheta
From the driagram of the entire system
costheta = √(L^2 - r^2) / L
So my answer depends on which equation i use. The second one is the correct one. How to know which equation we have to use? the answer for velocity is is also different for the two equations.
Is there something like i should only resolve one of these two? Because since tension's component is what i need to find centripetal force, i dont really need to resolve mg?