2. Sample Papers
  3. JEE Main & Advanced

JEE Main & Advanced Sample Paper JEE Main Sample Paper-30

  • question_answer
    The length of a needle floating, on the surface of water is \[2.25\,\,cm\]. The minimum force needed to lift the needle above the surface of water will be : \[(T=7.2\,N/cm)\]

    A)  \[3.6\,N\]                                

    B)  \[1.8\,N\]

    C)  \[72\,N\]                     

    D) \[18N\]

    Correct Answer: C

    Solution :

    At equilibrium of needle \[2TI=Mg\]. When we try to lift the needle up then force needed is equal to sum of weight of the needle and force due to surface   tension on the needle i.e. \[F=Mg+2Tl=2Tl=4Tl=4\times 7.2\times 2.5\]        


You need to login to perform this action.
You will be redirected in 3 sec spinner