1. The problem statement, all variables and given/known data A block of 1kg is resting on an incline of 20° that has a coefficient of friction μk=0.45 with the surface. It is connected with a mass less string to a friction-less pulley of mass 0.10 kg to a hanging block of 2 kg. What is the acceleration of the system without ignoring rotational inertia. Model the pulley as a disk. 2. Relevant equations First we need newtons 2nd law, ΣF=ma Also for rotational motion ΣF=Iα and friction is ƒk=μN where N is the normal force. 3. The attempt at a solution After drawing my free body diagrams, I was left with this : But I'm stumped there, I feel like I'm missing something obvious. I want to plug the two equations for the tensions into the pulley equation, but then I'm still missing the radius of the pulley. EDIT: The -m2g in the last equation on the right should be m2a EDIT #2: I forgot the R on the (T2-T1)=IAlpha, I solved it. Thanks.