Question

A body having specific charge $8\mu C/g$ is resting on a frictionless plane at a distance $10cm$ from the wall (as shown in the figure). It starts moving towards the wall when a uniform electric field of $100V/m$ is applied horizontally towards the wall.
If the collision of the body with the wall is perfectly elastic, then the time period of the motion will be ______ $s$.

Answer 1

Answer: 1

$F=ma$
$qE=ma$
$a=\frac{qE}{m}$
Now $d=\frac{1}{2}a{t}^2$
$t=\sqrt{\frac{2d}{a}}$
$t=\sqrt{\frac{2d}{\left(\frac{qE}{m}\right)}}$
$\therefore \frac{\left(\frac{8\times 10^{-6}}{10^{-3}}\right)\times 100}{2\times 0.1}$
$\therefore$ Time period $=2t=1sec$