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 will be ______.

Options

• q²Ey

• qEy

• qE²y

• qEy²

Answer 1

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 will be qEy.

Explanation:

Force on charged particle in a uniform electric field is

F = ma = Eq

or `a="Eq"/"m"`

From the equation of motion, we have

v2 = u2 + 2as `= 0 + 2xx"Eq"/"m"xx"y"="2Eqy"/"m"`

Now, kinetic energy of the particle

`"KE"=1/2"mv"^2="m"/2xx"2Eqy"/"m"="Eqy"`