Q151 / 180 · KCET 2019 · Physics

Two particles which are initially at rest move towards each other under the action of their
mutual attraction. If their speeds are \( v \) and \( 2 v \) at any instant, then the speed of center of mass
of the system is,

  • A
    \( 1.5 \mathrm{v} \)
  • B
    \( 2 \mathrm{v} \)
  • C
    \( \mathrm{v} \)
  • Correct answer
    D
    zero

Solution

(D)
At initial position both \( A \) and \( B \) are at rest, hence, momentum is zero. It is given that no external force isacting on them.
So, momentum remains zero. Since mass cannot be zero, therefore velocity is zero.

Hence, the correct answer is option: 'D'.

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