The mass of body A is half the mass of rod B mA=‌
mB
2
Rod B and rod C are in equilibrium. So mB=mC Apply Newton's law of motion. 2T−mAg=mAa‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(I) And, (mB+mC)g−2T‌‌=(mB+mC)a 2mBg−2T‌‌=2mBa 4mAg−2T‌‌=4mAa‌‌‌‌‌⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅⋅(II) Solve equation (I) and (II). a‌‌=‌