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

  • question_answer
    Two identical balls A and B are released from the positions shown in figure. They collide elastically on horizontal portion\[M/N\]. All surfaces are smooth. The ratio of heights attained by A and B after collision will be  

    A) \[1:4\]

    B) \[2:1\]                           

    C) \[4:13\]

    D) \[2:5\]

    Correct Answer: C

    Solution :

    [c] After collision, balls exchange their velocities
    \[\therefore \] \[{{V}_{A}}=\sqrt{2gh}\]  and  \[{{V}_{B}}=\sqrt{2g(4h)}=2\sqrt{2gh}\]
    Height gained by A will be  \[{{h}_{A}}=h\]
    But path of B will be first straight line and then parabolic as shown in figure
    After calculation, we can show that \[{{h}_{B}}=\frac{13}{4}h\]
    \[\therefore \]      \[\frac{{{h}_{A}}}{{{h}_{B}}}=\frac{4}{13}\]

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