Ok, it's 3am and I can't seem to get the answer that concurs with the answer in the back of the book, I went over my work 10 times and I don't see any mistakes in my work! 10. Two masses of 6 kg and 9 kg respectively are fastened to the pull ends of a cord passing over a light, frictionless pulley supported by a hook. Find the pull on the hook while the masses are in motion. Here's my work: Fnet = (M1 + M2)(A) Fnet = (-6 kg + 9 kg)(10 m/s^2) The 6 is negative because it's going upward (opposite to the 9, which is going downward) Fnet = 3(10m/s/s) Fnet = 30 N Now to find the acceleration of the system: As = Fnet / M1 + M2 As = 30 / 6 + 9 As = 30 / 15 As = 2m/s^2 We have the acceleration, now we just find the Tension between the first or second mass and the hook. Fnet = M1(As) Fg1 + FT = M1(As) Ft = M1(As) - Fg1 Ft = 6(2m/s^2) - (-60) Ft = 12 + 60 Ft = 72N It says the Answer should be 144N. Maybe I'm missing something because it's 3am, but please someone help? I'm dead tired and I have no idea what went wrong.