JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति Sample Paper Topic Test - Work Energy Power

  • question_answer
    Two blocks A and B of masses m and 2m placed on a smooth surface are travelling in opposite directions with velocities of 6 m/s and 4 m/s respectively. A perfectly elastic spring is attached to block A. If after collision, velocity of A is \[\frac{2}{3}\,\,m/s\] towards right , then velocity of block B would be

    A) \[\frac{4}{3}\,m/s\] towards left  

    B) \[\frac{16}{3}\,m/s\]  towards left

    C) \[\frac{28}{3}\,m/s\] m/s towards left

    D)  4 m/s towards left

    Correct Answer: C

    Solution :

    [c] Collision is elastic. Hence,
      or  \[V_{2}^{'}-\frac{2}{3}=-6-4\]
      \[P{{I}_{2}}=\frac{3}{2}\times 20=30cm\]  \[V_{2}^{'}=-10+\frac{2}{3}=-\frac{28}{3}m/s\]
      or velocity of B is \[{{P}^{2}}=P_{1}^{2}+P_{2}^{2}+2{{P}_{1}}{{P}_{2}}\cos \theta \] towards left.

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