1. The problem statement, all variables and given/known data Wasnt able to upload file, therefore an external link https://drive.google.com/file/d/0B0FIIKckKOcKWFcxcmtJRVRXZTA/view?usp=drivesdk A force F= mg is applied on C, all pullies are frictionless and we need to find the reading of the spring balance, basically the tension in it. 2. Relevant equations F=ma 3. The attempt at a solution I assumed the pulley and block A are moving downwards with an acceleration a1, then used pseudo forces to calculate acceleration of B and C which comes out to be g/2. Then I used the equation for A Tspring - 2mg=2ma1. I need another equation relating tension in spring to that in wire connecting B and C. 2Twire=Tspring? Or i can consider the mass of pulley as that of the blocks combined which gives me 2Twire - Tspring=2ma1? The pulley is massless, though.