In the diagram, the pulleys and the strings are massless. The strings do not stretch. The masses of the suspended blocks are m1 and m2, as shown. The magnitudes of the accelerations of the blocks are a1 and a2, respectively. I'm having trouble assigning the conventions for the variables. I assigned the motion downwards as positive. 1. The problem statement, all variables and given/known data T1 = The string connecting m2, and the string connecting the two pulleys. T2 = Left string connecting the left pulley. a1 = acceleration of mass 1 a2 = acceleration of mass 2 m2 m1 2. Relevant equations Result of FBD: T1 + m2g = m2a2 T2 + T1 - m1g = - m1a1 3. The attempt at a solution So... I can't isolate a1 in terms of a2.