There is given an ideal capacitor. The capacitor consists of two plates at a distance of $1mm.$ In a Cartesian coordinate system the plates are parallel to the $(x,y)$ plane.

The capacitor will be charged such that an electrical energy of ${10}^{-7}J$ will be stored in the capacitor and then it will be disconnected from the voltage source. You know that the stored energy $W$ of a capacitor is given by $W=\frac{1}{2}QU$ where $Q$ is the stored charge and $U$ is the applied voltage.

Now you bring in a dielectric material with a relative dielectric constant of $3$ which exactly fits between the two plates. You bring in the dielectric material by moving it without friction along the $x-$axis. The dielectric material has a mass of $10g.$

What will be the velocity $U_D$ of the dielectric material just at that moment when it is completely between the two plates of the capacitor?

$u_D=245\frac{mm}{s}$

$v_D=46,4\frac{mm}{s}$

$u_D=3650\frac{m}{s}$

$u_D=355\frac{m}{s}$

$u_D=7,81*{10}^{-3}\frac{m}{s}$

$u_D=4,52\frac{mm}{s}$

$u_D=7,96*{10}^{-3}\frac{m}{s}$

$u_D=2,31*{10}^{-3}\frac{m}{s}$

$u_D=88,2*{10}^{-3}\frac{m}{s}$

$u_D=26,3*{10}^{-3}\frac{m}{s}$