NEET Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति NEET PYQ-Work Energy Power and Collision

  • question_answer
    If kinetic energy of a body is increased by 300% then percentage change in momentum will be: [AIPMT 2002]

    A) 100%

    B) 150%

    C) 265%

    D) 73.2%

    Correct Answer: A

    Solution :

    Key idea: The relation between momentum p and kinetic energy K is \[K=\frac{1}{2\,m}({{p}^{2}})\]
                Kinetic energy \[K=\frac{1}{2m}({{p}^{2}})\]
                or         \[p=\sqrt{2m\,K}\]
                If kinetic energy of a body is increased by 300%, let its momentum becomes p’.
                New kinetic energy
                            \[K'=K+\frac{300}{100}K=4K\]
                Therefore, momentum is given by
                            \[p'=\sqrt{2m\times 4K}=2\sqrt{2mK}=2p\]
                Hence, % change (increase) in momentum
                            \[\frac{\Delta p}{p}\times 100=\frac{p'-p}{p}\times 100%\]
                            \[=\left( \frac{p'}{p}-1 \right)\times 100%\]
                            \[=\left( \frac{2p}{p}-1 \right)\,\times 100%\]
                            \[=100%\]


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