Question

The Young's modulus of a steel wire of length $6 m$ and cross-sectional area $3 \,mm ^2$, is $2 \times 10^{11}$ $N / m ^2$ 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 $\frac{1}{4}$ of its value on the earth The elongation of wire is (Take $g$ on the earth $=10\, m / s ^2$ ) :

• A. $0.1\,cm$
• B. $1 \,mn$
• C. $1 \,cm$
• D. $0.1 \,mm$

Answer 1

Answer: (A)

$0.1\,cm$

Answer 2

Tension (F)=mg
=4×410​=10N
ΔL=AYFL​
=3×10−6×2×101110×6​
=10−4m=0.1mm