BCECE Engineering BCECE Engineering Solved Paper-2006

  • question_answer
    A particle executes SHM of amplitude 25 cm and time period 3 s. What is the minimum time required for the particle to move between two points 12.5 cm on either side of the mean position?

    A)  0.5s                                      

    B)         1.0s

    C)         1.5s                                      

    D)         2.0s

    Correct Answer: A

    Solution :

    In order to find the time taken by the particle from \[-12.5\,cm\]to \[+\text{ }12.5\,cm\]on either side of mean position, we will find the time taken by particle to go from \[x=-12.5\,cm\]to \[x=\text{0}\]and to go from \[x=0\]to\[~x=+\text{ }12.5\,cm.\] Let the equation of motion be \[x=A\sin \omega t.\] First, the particle moves from \[x=-12.5\,cm\]to\[x=0\] \[\therefore \]  \[12.5=25\sin \omega t\]   \[(\because \,A=25\,cm)\] \[\Rightarrow \]               \[\frac{1}{2}=\sin \omega t\] \[\Rightarrow \]               \[\omega t=\frac{\pi }{6}\] \[\therefore \]  \[t=\frac{\pi }{6\omega }\] Similarly to go from \[x=0\]to \[x=12.5\,cm\] \[\omega t=\frac{\pi }{6}\]                 \[\Rightarrow \]                               \[t=\frac{\pi }{6\omega }\] \[\therefore \] Total time taken from \[x=-12.5\text{ }cm\]to                                 \[x=12.5\,cm\]                 \[t=\frac{\pi }{6\omega }+\frac{\pi }{6\omega }=\frac{\pi }{3\omega }\]             \[=\frac{\pi }{3\left( \frac{2\pi }{T} \right)}=\frac{T}{6}=\frac{3}{6}=0.5\,s\]


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