JEE Main & Advanced Physics Work, Energy, Power & Collision / कार्य, ऊर्जा और शक्ति JEE PYQ - Work Energy Power and Collision

  • question_answer
    This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements.      
    If two springs \[{{S}_{1}}\] and \[{{S}_{2}}\] of force constants \[{{k}_{1}}\]and \[{{k}_{2}}\], respectively, are stretched by the same force, it is found that more work is done on spring \[{{S}_{1}}\] than on spring \[{{S}_{2}}\].
    Statement 1: If stretched by the same amount, work done on \[{{S}_{1}}\], will be more than that on \[{{S}_{2}}\]
    Statement 2:  \[{{k}_{1}}<{{k}_{2}}\]                      [AIEEE 2012]

    A) Statement 1 is false, Statement 2 is true.

    B) Statement 1 is true, Statement 2 is false

    C) Statement 1 is true, Statement 2 is true, and Statement 2 is the correct explanation for statement 1

    D) Statement 1 is true, Statement 2 is true, and Statement 2 is not the correct explanation of Statement 1

    Correct Answer: A

    Solution :

    [a] \[{{k}_{1}}{{x}_{1}}={{k}_{2}}{{x}_{2}}=F\]
    \[{{W}_{1}}=\frac{1}{2}\,\,{{k}_{1}}{{x}_{1}}^{2}=\frac{{{({{k}_{1}}{{x}_{1}})}^{2}}}{2{{k}_{1}}}=\frac{{{F}^{2}}}{2{{k}_{1}}}\]
    Similarly \[{{W}_{2}}=\frac{{{F}^{2}}}{2{{k}_{2}}}\]           \[\Rightarrow \]   \[W\propto \frac{1}{k}\]
    \[{{W}_{1}}>{{W}_{2}}\]       \[\Rightarrow {{k}_{1}}<{{k}_{2}}\] statement-2 is true.
                Statement-1       \[{{W}_{1}}=\frac{1}{2}{{k}_{1}}\,{{x}^{2}}\]
                                        \[{{W}_{2}}=\frac{1}{2}{{k}_{1}}\,{{x}^{2}}\]
    So, \[{{W}_{2}}>{{W}_{1}}\]
    Statement-1 is false.


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