A block of mass $m$ containing a net negative charge $-q$ is placed on a frictionless horizontal table and is connected to a wall through an unstretched spring of spring constant $k$ as shown. If horizontal electric field $E$ parallel to the spring is switched on, then the maximum compression of the spring is :-
A$ \sqrt {qE / k}$
B$ \sqrt {k / qE}$
C$qE/k$
D$\frac{2qE}{k}$
Medium
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D$\frac{2qE}{k}$
d At the point of max compression
Work done by spring $=$ Potential due to the charge
$W_{\text {spring}}=V_{q}$
$\frac{1}{2} k x^{2}=E q$
$x=\sqrt{\frac{2 E q}{k}}$
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