Two wires each of radius 0.2 cm and negligible mass, one made of steel and other made of brass are loaded as shown in the figure. The elongation of the steel wire is ____×10−6m. [Young's modulus for steel =2×1011Nm−2 and g=10ms−2]
Answer: 20
Solution
The steel wire carries the 2 kg block together with the brass wire and the 1.14 kg block hanging below it, so its tension is T=(2+1.14)g=31.4 N. The cross-section is A=πr2=π(0.2×10−2)2=4π×10−6m2. The elongation follows ΔL=AYTL=4π×10−6×2×101131.4×1.6≈2.0×10−5 m. The elongation of the steel wire is 20×10−6 m.
