$A$ particle of charge $q$ and mass $m$ starts moving from the origin under the action of an electric field $\vec E = E\hat i$ and a magnetic field $\vec B = B\hat i$ with an initial velocity $\vec v = v_0\hat j$. The speed of the particle will become $2v_0$ after a time:

  • A
    $t = \frac{2mv_0}{qE}$
  • B
    $t = \frac{2Bq}{mv_0}$
  • C
    $t = \frac{\sqrt{3}Bq}{mv_0}$
  • D
    $t = \frac{\sqrt{3}mv_0}{qE}$

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