Question

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 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. Find the maximum load that can be put on the hanger without breaking a wire. Which wire break first if the load is increased ?

Answer 1

Let T₁ be the tension in the upper string and T₂ on lower string. Let m be the new mass. 

On upper string 

Substituting the values we have, 

m_max = 18 kg

Further on lower string 

Substituting the values we have,

m_max = 14 kg

Lower of the two is 14 kg, therefore answer is 14 kg.