Physics

Problem

A particle of mass

m

and charge

q

starts moving from the origin under the action of an electric field

\vec{E} = E\hat{i}

and magnetic field

\vec{B} = B\hat{i}

with a velocity

\vec{v} = v_0\hat{j}

. The speed of the particle becomes

2v_0

after a time

t

. Then

t

equals (A)

2 \left( \frac{mv_0}{qE} \right)

(B)

2 \left( \frac{m}{qB} \right)

(C)

\sqrt{3} \left( \frac{m}{qB} \right)

(D)

\sqrt{3} \left( \frac{mv_0}{qE} \right)