NEET Sample Paper NEET Sample Test Paper-19

  • question_answer A block attached to a spring, pulled by a constant horizontal force, is kept on a smooth surface as shown in the figure. Initially, the spring is in the natural state. Then the maximum positive work that the applied force F can do is (given that string does not break)

    A)  \[\frac{{{F}^{2}}}{K}\]                                  

    B) \[\frac{2{{F}^{2}}}{K}\]

    C)  \[\infty \]                                  

    D) \[\frac{{{F}^{2}}}{2K}\] 

    Correct Answer: B

    Solution :

    For maximum positive work the final speed must be zero. Let the extension in the spring be 1. Applying work-energy theorem on the block,  we get\[F\ell -\frac{1}{2}k{{\ell }^{2}}=0\] \[\ell =\frac{2F}{k}\]or work done \[=F\ell =\frac{2{{F}^{2}}}{k}\] Hence, the correction option is [b].


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