Three equal weights A, B, C of mass 2 kg each are hanging on a string passing over a fixed frictionless pulley as shown in the fig. (3). The tension in the string connecting weights B and C is

T -2 g =2 a        For A ... (1)T1 + 2g-T=2a    For B ...(2)2g -T1 =2 a       For C ...(3)Adding eqs. (1) and (2), we get T1 = 4a                      …(4)From eqs. (3) and (4), 2g - 4a = 2a or a=(g/3) ...(5)Substituting the value of a from eq. (5) in eq. (4), we getT1 =4 x (g/3) =13N