Question

A particle of mass m and charge q is placed at rest in a uniform electric field e and then released.the kinetic energy attained by the particle after moving a distance y is

Answer 1

K.E. = Force x distance = qE.y

Answer 2

Answer:

Kinetic energy, KE = qEy

Explanation:

It is given that,

The mass of the particle is m having charge q is placed at rest in uniform electric field e and then released.

We have to find the kinetic energy attained by the particle after moving a distance y.

Using third equation of motion as :

$v^2-u^2=2as$

Here, u = 0 (particle is initially at rest)

s = y (displacement)

$v^2=2ay$.......(1)

Force on a particle in electric field is, F = qE

Since, F = ma

So, $a=\dfrac{qE}{m}$............(2)

Put the value of a in equation (1)

$v^2=2\dfrac{qEy}{m}$..................(3)

We know that kinetic energy of a particle is given by, $E_k=\dfrac{1}{2}mv^2$

Putting equation (3) in above equation.

$E_k=qEy$

Hence, this is the required solution.