Question

A particle having mass m and charge q is at rest. On applying a uniform electric field E on it, it starts moving. What is its kinetic energy when it travels a distance y in the direction of force ?(A) qE²y (B) qEy² (C) qEy (D) q²Ey

Answer 1

Answer:

correct option is the B

Explanation:

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Answer 2

Answer:

(C) qEy

Explanation:

Mass of the particle = m (Given)

Charge of the particle = q (Given)

Uniform electric field = E (Given)

According to the third equation of motion -

v² - u² = 2as

Where u = 0 as the particle is initially at rest and  s = y the displacement

Thus,

v² = 2ay ---- 1

Force on a particle in electric field is defined as - F = qE

Since, F = ma thus,

a = qE/m ---- 2

Substituting the value in first equation -

v² = 2. qEy/ m ----- 3

Kinetic energy = 1/2mv²

Substituting the value in third equation -

Ek = qEy