1. The problem statement, all variables and given/known data , the pulley, object a and object b all have the same mass The cylinder rotates without sliding He asked for the cylinder's acceleration in m(mass),g(gravitation), r(radius) variables 2. Relevant equations 3. The attempt at a solution Okay, so my teacher said that the frictional force oppose the line tension, Object 1(cylinder) [tex]\sum torque=(line tension2 . radius) - (frictionalforce . radius) = m.a[/tex] Pulley (line tension1-linetension2)xradius=1/2mr2 Object B Line tension1 - weight = m . a what I don't get is why my teacher said that object a's acceleration is the total of its tangential acceleration and its linear acceleration.