$A$ simple pendulum consists of a sphere with a mass of $8 \ \mu g$ and a charge of $39.2 \times 10^{-10} \ C$. When a horizontal electric field of $20 \times 10^3 \ V/m$ is applied,what angle (in degrees) does the string make with the vertical?

An electron enters an electric field with its velocity in the direction of the electric lines of force. Then:

If a particle of mass $10 \ mg$ and charge $2 \ \mu C$ at rest is subjected to a uniform electric field of potential difference $160 \ V$,then the velocity acquired by the particle is (in $ms^{-1}$)

If an electron and an $\alpha$-particle are accelerated under a potential difference of $100 \, V$, what is the ratio of their momenta?

In a certain region,a uniform electric field $E$ and a magnetic field $B$ are present in opposite directions. At the instant $t = 0$,a particle of mass $m$ carrying a charge $q$ is given a velocity $v_0$ at an angle $\theta$ with the $y$-axis,in the $yz$-plane. The time after which the speed of the particle would be minimum is equal to

An electron with mass $9.1 \times 10^{-31} \ kg$ and charge $1.6 \times 10^{-19} \ C$ is placed in an electric field of $1 \times 10^6 \ V/m$. How much time will it take for the electron to reach a velocity equal to $1/10$th of the speed of light?