NEET Physics Motion in a Straight Line / सरल रेखा में गति NEET PYQ-One Dimensional Motion

  • question_answer
    A ball of mass 2 kg and another of mass 4 kg are dropped together from a 60 feet tall building. After a fall of 30 feet each towards earth, their respective kinetic energies will be in the ratio of:                           [AIPMT (S) 2004]

    A) \[\sqrt{2}:1\]

    B) 1 : 4                 

    C) 1 : 2

    D) \[1:\sqrt{2}\]

    Correct Answer: C

    Solution :

    Key Idea: In a free fall, two balls of different mass will acquire the same velocity after falling through same height.
    From key idea, \[{{v}_{1}}={{v}_{2}}=v\] at a 30 feet from falling point.
    Here,     \[{{m}_{1}}=2kg,\,\,\,{{m}_{2}}=4kg\]
    Thus,     \[\frac{{{K}_{1}}}{{{K}_{2}}}=\frac{\frac{1}{2}{{m}_{1}}{{v}^{2}}}{\frac{1}{2}{{m}_{2}}{{v}^{2}}}=\frac{{{m}_{1}}}{{{m}_{2}}}=\frac{2}{4}=\frac{1}{2}\]


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