Hi! I’ve recently done an experiment that I didn’t completely understand and now it seems I’ve lost all my notes as well (the notes written down from the teacher’s board, with a formula I really need, but didn’t understand). This work is supposed to be completed during the summer holiday, so I can’t really ask my teacher for help, either. During the experiment, I was supposed to find gravity using “horizontal uniform circular motion.” I had two different masses attached to a piece of string and rotated one of the masses above my head while trying to make the other mass stay still. This is what I’ve managed to figure out this far: I believe T1 (in the part of the string not rotating) should be equal to T2 (the tension in the rotating string). X (T1) = 0 Y (T2) = m(1)*g X (T2) = T * sin(θ) = ((4*π^2*R)/T^2)*m(2) Y (T2) = T * cos(θ) = g * m (2) I did not calculate θ as my teacher said it would not be necessary. This is the point where I think I’m starting to get lost. I’ve got the different components, but I’m not sure how to combine them. I’ve no idea if this works at all: Y (T total) = g(M(1) – M(2)) X (T total) = ((4*π^2*R)/T^2)*m(2) And now for my question. I’m sorry, it might sound really stupid, but like I said I’m totally confused and this is my first year with physics, so please bear with me: Can I now assume that the Y-component of T total equals the X-component of T total? If not, how can I calculate T2? I thought of using the Pythagoras theorem, but it seemed like I would end up with g on both sides of my formula, and g is what I am supposed to calculate.