A body having specific charge $8\ \mu\text{C g}^{-1}$ is resting on a frictionless plane at a distance 10 cm from the wall (as shown in the figure). It starts moving towards the wall when a uniform electric field of $100\ \text{V m}^{-1}$ 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.
Numerical value type. Enter your answer.
Answer: 1
$\dfrac{q}{m} = 8\ \mu\text{C g}^{-1} = 8\times10^{-3}\ \text{C kg}^{-1}$, so $a = \dfrac{q}{m}E = 0.8\ \text{m s}^{-2}$.
Time to reach the wall: $t = \sqrt{\dfrac{2\times0.1}{0.8}} = 0.5$ s. After the elastic bounce the body decelerates and comes to rest at its starting point in another 0.5 s.
Period $= 1$ s.
Solution by Sreeraj P, M.Sc Physics