$A$ point charge $Q$ is fixed. $A$ small charge $q$ and mass $m$ is given a velocity $v_0$ from infinity at a perpendicular distance $r_0$ as shown. If the distance of closest approach is $r_0/2$,find the value of $q$. [Given $mv_0^2 = \frac{Q^2}{4\pi \epsilon_0 r_0}$]

  • A
    $q = - \frac{Q}{4}$
  • B
    $q = - \frac{Q}{2}$
  • C
    $q = - \frac{3Q}{4}$
  • D
    $q = - Q$

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