JEE Main & Advanced Sample Paper JEE Main Sample Paper-38

  • question_answer    The length of an elastic string is x when the tension is 5N. Its length is y when the tension is 7N. What will be its length, when the tension is 9N?                                

    A)  \[2y+x\]                      

    B)  \[2y-x\]

    C)  \[7x-5y\]                      

    D)  \[7x+5y\]

    Correct Answer: B

    Solution :

     We have, \[F=kx\] where, F, x and k are force, length and constant respectively.             \[\therefore \]      \[5=kx\]                                   ?.(1)             and      \[7=ky\]                                   ?.(2) Multiplying eq. (2) by 2 \[14=2ky\] Subtracting eq (1) from (3), \[14-5=2ky-kx\] or \[9=k(2y-x)\] Hence, required length \[=2y-x\]


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