J & K CET Medical J & K - CET Medical Solved Paper-2007

  • question_answer
    The coordinates of a moving particle at any time t are given by \[x=\alpha {{t}^{3}}\] and \[y=\beta {{t}^{3}}\]. The speed of the particle at time t is given by

    A) \[3t\sqrt{{{\alpha }^{2}}+{{\beta }^{2}}}\]                           

    B) \[3{{t}^{2}}\sqrt{{{\alpha }^{2}}+{{\beta }^{2}}}\]

    C)  \[{{t}^{2}}\sqrt{{{\alpha }^{2}}+{{\beta }^{2}}}\]                              

    D)  \[\sqrt{{{\alpha }^{2}}+{{\beta }^{2}}}\]

    Correct Answer: B

    Solution :

                     \[x=a{{t}^{3}},y=\beta {{t}^{3}}\] \[{{v}_{x}}=\frac{dx}{dt}=3\alpha {{t}^{2}}\] \[{{v}_{y}}=\frac{dy}{dt}=3\beta {{t}^{2}}\] Resultant velocity                 \[v=\sqrt{v_{x}^{2}+v_{y}^{2}}\]                 \[=\sqrt{9{{\alpha }^{2}}{{t}^{4}}+9{{\beta }^{2}}{{t}^{4}}}\]                 \[=3{{t}^{2}}\sqrt{{{\alpha }^{2}}+{{\beta }^{2}}}\]


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