NEET NEET SOLVED PAPER 2016 Phase-I

  • question_answer
    A particle moves so that its position vector is given by \[\overrightarrow{r}=\cos \,\omega \text{ }t\,\widehat{x}+\sin \,\omega \,t\,\widehat{y}.\] Where \[\omega \] is a constant.  Which of the following is true?                                                                                                                

    A)  Velocity and acceleration both are perpendicular to r \[\vec{r}.\]

    B)  Velocity and acceleration both are parallel to \[\vec{r}.\]

    C)   Velocity is perpendicular to \[\vec{r}.\]and acceleration is directed towards the origin

    D)   Velocity is perpendicular to \[\vec{r}.\]and acceleration is directed away from the origin

    Correct Answer: C

    Solution :

                     \[\vec{r}=\cos \omega t\,\hat{x}\,+sin\omega t\,\hat{y}\] \[\vec{v}=-\omega \sin \omega t\,\hat{x}+\omega \cos \omega t\,\hat{y}\] \[\vec{a}=-{{\omega }^{2}}\cos \omega t\,\hat{x}+\omega \sin \omega t\,\hat{y}=-{{\omega }^{2}}\vec{r}\] \[\vec{r}.\vec{v}=0\] hence \[\vec{r}\bot \vec{v}\]\[\vec{\alpha }\]is directed towards the origin.


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