1. The problem statement, all variables and given/known data http://imgur.com/ZkjXv The given answers are (b) .309 m/s^2 (c) T1= 7.67N, T2=9.22N 2. Relevant equations I_disc = .5(mass_disc)r^2 Sum of Torque = I α a = r α 3. The attempt at a solution We will define the system moving right and down as positive to get a positive acceleration. The tension between mass 1 (2kg) and the pulley is T_1 The tension between mass 2 (6kg) and the pulley is T_2 Summation of Torque = I α = rT_2 - rT_1 plug in: α = a/r and I_disc = .5(mass_disc)r^2 into I α = rT_2 - rT_1 to get a(.5)(mass_disc) = T_2 - T_1 The summation of the forces in the x-direction for m1 is: F_x = m1(a) = T_1 - μ(m1)g T_1 = (m1)a + μmg How do you define the summation of the forces for m2 and get an expression for T_2? My first attempt: Sum of Forces for M2 in x direction: F_x = (m2)a = T_2 - μ(m2)gcos30 T_2 = (m2)a + μ(m2)gcos30 is incorrect. This was done through rotating the system 30 degrees but the summation for mass 1 was not rotated therefore the equations are not consistent and apparently, wrong. What is the best way to do this?