Q.

The Young’s modulus of a steel wire of length 6 m and cross-sectional area 3 mm2 is 2×1011 N/m2. The wire is suspended from its support on a given planet. A block of mass 4 kg is attached to the free end of the wire. The acceleration due to gravity on the planet is 14 of its value on the Earth. The elongation of the wire is (Take g on the Earth =10 m/s2)                [2023]

1 1 cm  
2 1 mm  
3 0.1 mm  
4 0.1 cm  

Ans.

(3)

Tension (F)=mg=4×104=10 N

ΔY=FLAY=10×63×10-6×2×1011=10-4 m=0.1 mm