\(\frac {v}{2\sqrt 2}\)
\(\frac v2\)
\(\frac v4\)
\(\frac {v}{\sqrt 2}\)
∵ Loss in Kinetic Energy = Gain in spring energy
\(⇒\frac 12mv^2×2=\frac 12kx_m^2\)
\(⇒2×\frac 14×v^2=2×x_m^2\)
\(⇒x_m=\sqrt {\frac {v^2}{4}}\)
\(⇒x_m=\frac v2\)
So, the correct option is (B): \(\frac v2\)

Potential energy (V) versus distance (x) is given by the graph. Rank various regions as per the magnitudes of the force (F) acting on a particle from high to low. 
Which one of the following graphs accurately represents the plot of partial pressure of CS₂ vs its mole fraction in a mixture of acetone and CS₂ at constant temperature?

In the given figure, the blocks $A$, $B$ and $C$ weigh $4\,\text{kg}$, $6\,\text{kg}$ and $8\,\text{kg}$ respectively. The coefficient of sliding friction between any two surfaces is $0.5$. The force $\vec{F}$ required to slide the block $C$ with constant speed is ___ N.
(Given: $g = 10\,\text{m s}^{-2}$) 
Read More: Work and Energy