NEET NEET SOLVED PAPER 2017

  • question_answer
    A spring of force constant k is cut into lengths of ratio 1 : 2 : 3. They are connected in series and the new force constant is k?. Then they are connected in parallel and force constant is k?. Then k? : k?? is             

    A)  1 : 14                    

    B)  1 : 6

    C)  1 : 9                                      

    D)   1 : 11

    Correct Answer: D

    Solution :

    Spring constant\[\propto \frac{\text{1}}{\text{length}}\] \[k\propto \frac{1}{l}\] i.e,          \[{{k}_{1}}=6k\] \[{{k}_{2}}=3k\] \[{{k}_{3}}=2k\] In series \[\frac{1}{k'}=\frac{1}{6k}+\frac{1}{3k}+\frac{1}{2k}\] \[\frac{1}{k'}=\frac{6}{6k}\] \[k'=k\] \[k''=6k+3k+2k\] \[k''=11k\] \[\frac{k'}{k''}=\frac{1}{11}\]i. e \[k':k''=1:11\]


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