$A$ proton of mass $m$ and charge $e$ is projected from a very large distance towards an $\alpha$-particle with velocity $v$. Initially,the $\alpha$-particle is at rest,but it is free to move. If gravity is neglected,then the minimum separation along the straight line of their motion will be:

  • A
    $e^2 / 4 \pi \varepsilon_0 m v^2$
  • B
    $5 e^2 / 4 \pi \varepsilon_0 m v^2$
  • C
    $2 e^2 / 4 \pi \varepsilon_0 m v^2$
  • D
    $4 e^2 / 4 \pi \varepsilon_0 m v^2$

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