Two particles $A$ and $B,$ move with constant  velocities $\vec v_1$ and $\vec v_2$. At the initial moment their position vectors are $\vec r_1$ and $\vec r_2$ respectively. The condition for particles $A$ and $B$ for their collision is

  • [AIPMT 2015]
  • A

    $\frac{{\overrightarrow {{r_1}} - \overrightarrow {{r_2}} }}{{\left| {\overrightarrow {{r_1}} - \overrightarrow {{r_2}} } \right|}} = \;\frac{{\overrightarrow {{v_2}} - \overrightarrow {{v_1}} }}{{\left| {\overrightarrow {{v_2}} - \overrightarrow {{v_1}} } \right|}}\;\;\;$

  • B

    $\overrightarrow {{r_1}} $ -$\overrightarrow {{r_2}} $ = $\overrightarrow {{v_1}} $ -$\overrightarrow {{v_2}} $

  • C

    $\;\overrightarrow {{r_1}} $ .$\;\overrightarrow {{v_1}} $ =$\overrightarrow {{r_2}} $ .$\;\overrightarrow {{v_2}} $

  • D

    $\;\overrightarrow {{r_1}} \times \overrightarrow {{v_1}}=\overrightarrow {{r_2}}  \times \overrightarrow {{v_2}} $

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