NEET Sample Paper NEET Sample Test Paper-24

  • question_answer
    A rectangular block of mass m and area of cross-section A floats in a liquid of density \[\rho .\] If it is given a small vertical displacement from equilibrium it undergoes oscillation with a time period T then:

    A)  \[T\propto \sqrt{\rho }\]             

    B)  \[T\propto \frac{1}{\sqrt{A}}\]

    C)  \[T\propto \frac{1}{\rho }\]                    

    D)  \[T\propto \frac{1}{\sqrt{m}}\]

    Correct Answer: B

    Solution :

     Force applied on the body will be equal to upthrust for vertical oscillations. Let block is displaced through\[x\]m, then the weight of displaced water or upthrust (upwards) \[=-Ax\rho g\] Where A is area of cross-section of the block and \[\rho \]is its density. This must be equal to force (= md) applied, where m is mass of the block and a is acceleration. \[\therefore \]      \[ma=-Ax\rho g\] or         \[a=-\frac{A\rho g}{m}x=-{{\omega }^{2}}x\] This is the equation of simple harmonic motion. Time period of oscillation \[T=\frac{2\pi }{\omega }=2\pi \sqrt{\frac{m}{A\rho g}}\Rightarrow T\propto \frac{1}{\sqrt{A}}\]


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