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  • The elastic potential energy stored in a steel wire of length 20 m stretched through 2 cm is 80 J. The cross sectional area of the wire is ___________ mm2. <img alt="\text { (G

The elastic potential energy stored in a steel wire of length 20 m stretched through 2 cm is 80 J. The cross sectional area of the wire is ___________ mm2.

\text { (Given, } \mathrm{y}=2.0 \times 10^{11} \mathrm{Nm}^{-2} \text { ) }

Option: 1

40


Option: 2

-


Option: 3

-


Option: 4

-


Answers (1)

best_answer

\begin{aligned} & \text { Energy, } \mathrm{U}=\frac{1}{2} \mathrm{kx}^2 \\ & 80=\frac{1}{2} \mathrm{k}\left(2 \times 10^{-2}\right)^2 \\ & \mathrm{k}=\frac{160}{4 \times 10^{-4}} \\ & \mathrm{k}=4 \times 10^5 \mathrm{~N} / \mathrm{m} \\ & \frac{\mathrm{yA}}{\ell}=4 \times 10^5 \end{aligned}

\begin{aligned} & \mathrm{A}=\frac{4 \times 10^5 \times 20}{2 \times 10^{11}} \\ & \mathrm{~A}=40 \times 10^{-6} \mathrm{~m}^2 \\ & \mathrm{~A}=40 \mathrm{~mm}^2 \end{aligned}

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