JEE Main & Advanced Physics Simple Harmonic Motion Question Bank Critical Thinking

  • question_answer
    A particle executes simple harmonic motion (amplitude = A) between \[x=-A\] and \[x=+A\]. The time taken for it to go from 0 to A/2 is \[{{T}_{1}}\] and to go from A/2 to A is \[{{T}_{2}}\]. Then  [IIT-JEE (Screening) 2001]

    A)            \[{{T}_{1}}<{{T}_{2}}\]     

    B)            \[{{T}_{1}}>{{T}_{2}}\]

    C)            \[{{T}_{1}}={{T}_{2}}\]     

    D)            \[{{T}_{1}}=2{{T}_{2}}\]

    Correct Answer: A

    Solution :

                       Using \[x=A\sin \omega t\] For \[x=A/2,\ \ \sin \omega {{T}_{1}}=1/2\Rightarrow {{T}_{1}}=\frac{\pi }{6\omega }\] For \[x=A,\ \sin \omega ({{T}_{1}}+{{T}_{2}})=1\Rightarrow {{T}_{1}}+{{T}_{2}}=\frac{\pi }{2\omega }\] \[\Rightarrow {{T}_{2}}=\frac{\pi }{2\omega }-{{T}_{1}}=\frac{\pi }{2\omega }-\frac{\pi }{6\omega }=\frac{\pi }{3\omega }i.e.\ {{T}_{1}}<{{T}_{2}}\] Alternate method : In S.H.M., velocity of particle also oscillates simple harmonically. Speed is more near the mean position and less near the extreme position. Therefore the time taken for the particle to go from 0 to \[\frac{A}{2}\] will be less than the time taken to go from \[\frac{A}{2}\] to A. Hence \[{{T}_{1}}<{{T}_{2}}.\]


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