Given:
Mass of the particle : m= 1g = 10^-3 kg
Charge of the particle: q = 2.5 × 10^–4 C
Electric Field: E = 1.2 × 10⁴ N C^–1
Distance travelled : s = 40 cm = 0.4 m
Initial velocity: u = 0
Formula used:

(a)
When a charge q moves in an uniform electric field E, it experiences an electric force F_e.
F_e = qE
substituting the values we get,
∴ F_e = 3N
Force of gravity would be:
Where m is the mass of the particle and g is the acceleration due to gravity.

Since the mass of the particle is very low, force due to gravity can be neglected.
(b)
From Newton’s Second Law,
F=ma
where a is the acceleration of the body and m is the mass.
acceleration of the particle is:


Here, s is the distance travelled, u is the initial velocity, t is the time required to travel s, and a is the acceleration of the particle.
Substituting we get,



It will take 0.0163 seconds for the particle to travel a distance of 40 cm.
(c)
Using another equation of motion
Here v is the final velocity of the particle,u is the initial velocity of the particle, a is the acceleration and s is the distance travelled by the particle.
Substituting we get,


After travelling 40cm the speed of the particle will be 48.9 m/s.
(d)
We know that,
Work=Force×Displacement
Thus work done by the electric force:
W = F × s
∴ W = 3× 0.4
∴ W = 1.2 J

Hence , work of 1.2 J is being done by the electric force on the particle.