Answer 1

Given:
Charge of the particle, q = 2.5 × 10⁻⁴ C
Initial velocity, u = 0 
Electric field intensity, E = 1.2 × 10⁴ N/C
Mass of the particle, m = 1 g = 10⁻³ kg
Distance travelled, s = 40 cm = 4 × 10⁻¹ m

Acceleration of the particle, 

\[a = \frac{F_e}{m} = \frac{3}{{10}^{- 3}} = 3 \times  {10}^3  \text{ m/ s}^2\]

Let t be the time taken by the particle to cover the distance s = 40 cm. Then,

\[s = \frac{1}{2}a t^2 \] 

\[ \Rightarrow   t = \sqrt{\frac{2s}{a}} = 1 . 63 \times  {10}^{- 2}   s\]