A block of weight 100 N is suspended by copper and steel wires of same cross-sectional area 0.5 c m 2 and,…

A block of weight 100 N is suspended by copper and steel wires of same cross-sectional area 0.5 cm2 and, length 3 m and 1 m, respectively. Their other ends are fixed on a ceiling as shown in figure. The angles subtended by copper and steel wires with ceiling are 30o and 60o, respectively. If elongation in copper wire is ΔlC and elongation in steel wire is ΔlS, then the ratio ΔlCΔlS is _____.
[Young's modulus for copper and steel are 1×1011N/m2 and 2×1011N/m2 respectively]

Solution

2.00

Resolving in components
Fx=0
TScos60=TCcos30
TS12=TC32
TS=3TC
ΔlCΔlS=TClCTSlSYS
ΔlCΔlS=TCTSlClSYSYC=13312×10111×1011=2

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Asked in: JEE Advanced 2019 (Paper 1)

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