The mass of charge $Q$ is $m$ and the mass of charge $2Q$ is $4m$. If both are released from rest at an initial separation $r$,what will be the kinetic energy $(K.E.)$ of charge $Q$ at infinite separation?

$A$ point charge $2 \times 10^{-2} \, C$ is moved from $P$ to $S$ in a uniform electric field of $30 \, N C^{-1}$ directed along the positive $x$-axis. If the coordinates of $P$ and $S$ are $(1, 2, 0) \, m$ and $(0, 0, 0) \, m$ respectively,the work done by the electric field will be $......... \, mJ$.

$A$ ball of mass $1 \, g$ and charge $10^{-8} \, C$ moves from point $A$ $(V_A = 600 \, V)$ to point $B$ where the potential is zero. The velocity of the ball at point $B$ is $20 \, cm/s$. Find the velocity of the ball at point $A$ in $cm/s$.

The distance between the plates of a capacitor is $1 \ mm$. An electric field of $5 \times 10^5 \ V/m$ is produced between the two plates. What will be the change in the potential energy $(PE)$ of an electron if it is moved from one plate to the other?

$A$ ball of mass $1\, g$ and charge $10^{-8}\ C$ moves from point $A$ at a potential of $600\, V$ to point $B$ at a potential of $0\, V$. If the velocity of the ball at point $B$ is $20\, cm/s$,then the velocity of the ball at point $A$ is . . . . . . $cm/s$.

$A$ particle $A$ has charge $+q$ and a particle $B$ has charge $+4q$,with each of them having the same mass $m$. When allowed to fall from rest through the same electric potential difference,the ratio of their speeds $\frac{v_A}{v_B}$ will be: