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PART - 1 CH - 5Work, Energy and Power — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsPART - 1 CH - 5Work, Energy and Power2 Marks
Question
The length of steel wire got increases by 0.25 cm by hanging a weight of 2.5 kg . Find the work done in pulling the wire $\left(g=10 m / s ^2\right)$
✓

Answer

It is given,
$\therefore \quad \begin{aligned}
M & =2.5 kg wt \\
Mg & =2.5 \times 10=25 \\
x & =0.25 cm \\
& =\frac{0.25}{100} m
\end{aligned}$
From formula, $Mg =k x$
$\begin{aligned}
k & =\frac{Mg}{x}=\frac{25}{\frac{0.25}{100}} \\
& =\frac{2.5 \times 100}{0.25}=10000 N / m=10^4 N / m
\end{aligned}$
Work done in pulling the wire,
$\begin{aligned}
W & =\frac{1}{2} k x^2 \\
W & =\frac{1}{2} \times 10^4 \times\left(\frac{0.25}{100}\right)^2 \\
W & =\frac{1}{2} \times(0.25)^2=\frac{1}{2} \times 0.0625 \\
& =0.03125 J \quad Ans.
\end{aligned}$

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