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5.Work, Energy, Power and Collision
easy
A mass of $1\, kg$ is hanging from a spring of spring constant $1\, N/m$. If Saroj pulls the mass down by $2\,m$. The work done by Saroj is......$J$
A
$1$
B
$2$
C
$3$
D
$4$
(AIIMS-2009)
Solution
$\begin{gathered}
Work\,done = \left[ {\int\limits_0^2 {F.dx} = \,\int\limits_0^2 {kx\,dx\, = \frac{1}{2}k{x^2}} } \right]_0^2 \hfill \\
\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \,\frac{1}{2}.1.\left( {4 – 0} \right) = 2\,J \hfill \\
\end{gathered} $
Standard 11
Physics
