So I've been prepping for my Engineering Physics 1 final, and I've been having trouble with rotational motion problems, but this problem has been driving me crazy for the past two days: 1. The problem statement, all variables and given/known data (I wanted to include a normal link to an image, but I'm a new member, so here's something) i.imgur.com/wHAG3.jpg There are two masses, one on top of a frictionless tabletop (12.0 kg), and one hanging off the edge of the table (5.00 kg), both are connected by an ideal cord wrapped around a frictionless pulley with a radius of 0.26 m and a mass of 2.10 kg. What are the respective tensions of the horizontal and vertical segments of the cord? Known variables: mass on top of table = 12.0 kg mass hanging off edge = 5.00 kg radius of pully = 0.26 m mass of pully = 2.10 kg Unknowns: Horizontal Tension Vertical Tension 2. Relevant equations I = 1/2*m*r2 (moment of intertia) τ = I*αθ (Torque, and that's angular acceleration on the right) Krot = 1/2*I*ω2 (rotational kinetic energy) F = m*a 3. The attempt at a solution I first attempted to find the torque on the disk and translate that into tangential force on the mass on the table. After that failed I thought that the acceleration for everything in the system should be the same and tried to make acceleration equations for the two masses and the pulley and solve with algebra. Both gave me incorrect answers. I'm not sure whether I'm approaching this incorrectly or if the equations I set up were wrong. Thanks in advance!