Manipal Engineering Manipal Engineering Solved Paper-2013

  • question_answer
    A wet open umbrella is held vertical and it whirld about the handle at a uniform rate of 21 revolutions in\[44s\]. If the rim of the umbrella is circle of\[1m\]in diameter and the height of the rim above the flour is\[4.9m\], the locus of the drop is a circle of radius

    A) \[\sqrt{2.5}m\]                

    B) \[1\,\,m\]

    C) \[3\,\,m\]                           

    D)        \[1.5\,\,m\]

    Correct Answer: A

    Solution :

    From equation of motion                 \[h=ut+\frac{1}{2}g{{t}^{2}}\] where\[u\] is initial velocity and \[t\] time. Since,\[u=0\] \[\therefore \]  \[t=\sqrt{\frac{2h}{g}}=\frac{\sqrt{2\times 4.9}}{9.8}=1\,\,s\] The horizontal range of the drop\[=x\], then                 \[x=\left( \frac{{{v}_{t}}}{o} \right)t\] Also,     \[\omega =\frac{\Delta \theta }{\Delta t}=\frac{21\times 2\pi }{44}=3\,\,rad/s\] Tangential speed\[{{v}_{t}}=r\omega =0.5\times 3\times 1.5\,\,m/s\] \[x=1.5\times 1=1.5m\] Locus of drop\[=\sqrt{{{x}^{2}}+{{r}^{2}}}=\sqrt{{{(1.5)}^{2}}+{{(0.5)}^{2}}}\]                          \[=\sqrt{2.5}m\]


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