The two wires shown in figure are made of the same material which has a breaking stress of 8 x 108 N/m2. The area of the cross-section of the upper wire is 0.006 cm2 and that of the lower wire is 0.003 cm2. The mass m1 = 10 kg, m2 = 20 kg and the hanger is light. The maximum load that can be put on the hanger without breaking a wire is

Let load put on the hanger is F, then stress in lower wireS1 = m1g+F0.003×10-4Let S1 = 8 × 108 N/m2, then  8×108 = 10×10+F3×10-7  ⇒F =140 NLet stress developed in upper wire is S2, thenS2 = (m1+m2)g+F0.006×10-4Let S2 = 8 × 108 N/m28×108 = (10+20)10+F6×10-7 ⇒ F = 180 NWe have to select the lower value of F. Hence maximum load that can be suspended is 140g = 14 kg .