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Question 30556
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Center of Mass, Momentum and Collision: JEE — COM Frame KE MCQ

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JEE — COM Frame KEHardQuestion 30556

Question

For two particles, the total kinetic energy measured in the centre-of-mass frame is:
  1. A
    The kinetic energy of their relative motion
    Correct
  2. B
    Always zero
  3. C
    ½(m₁+m₂)v_cm²
  4. D
    Always greater than the laboratory-frame KE

Correct answer

The kinetic energy of their relative motion

Explanation

Removing the centre-of-mass motion leaves only relative motion. For two particles, KCOM=12μvrel2K_{COM}=\frac12μv_{rel}^2, where μμ is the reduced mass.

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