JEE Main & Advanced Sample Paper JEE Main Sample Paper-19

  • question_answer 52)
    DIRECTIONS (Qs 52): Read the following passage and answer the questions that follows
    A block of mass \[15\text{ }kg\] is placed over a frictionless horizontal surface. Another block of mass \[10\text{ }kg\] is placed over it, that is connected with a light string passing over two pulleys fastened to the \[15\text{ }kg\] block. A force \[F=80N\]is applied horizontally to the free end of the string. Friction coefficient between two blocks is\[0.6\]. The portion of the string between \[10kg\] block and the upper pulley is horizontal. Pulley string and connecting rods are massless. (Take \[g=10\text{ }m/{{s}^{2}}\])
    If applied force \[F=120\text{ }N,\]then magnitude of acceleration of \[15\text{ }kg\] block will be-

    A)  \[8\text{ }m/{{s}^{2}}\]                     

    B)  \[4\text{ }m/{{s}^{2}}\]

    C)  \[\text{3}\text{.2 }m/{{s}^{2}}\]                     

    D)  \[\text{4}\text{.8 }m/{{s}^{2}}\]

    Correct Answer: B

    Solution :

     If \[F=120N,\] then there will be slipping, so using FBDs of both (friction will be 60 N) For \[10\,kg\]block, \[120-60=10a\Rightarrow a=6\,m/{{s}^{2}},\] For \[15\text{ }kg\] block, \[60=50a\Rightarrow a=4m/{{s}^{2}}\].

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