NEET-XI-Physics

exam-1 year:2016

with Solutions - page 2
  • #27
    A particle moves so that its position vector is given
    by ``\vec{r}`` = ``cos\omega``t ``\hat{x}`` + ``sin\omega``t ``\hat{y}`` .
    Where ``\omega`` is a constant.
    Which of the following is true ?
    (1) Velocity and acceleration both are perpendicular
    to ``\vec{r}``.
    (2) Velocity and acceleration both are parallel to r``\vec{r}``
    (3) Velocity is perpendicular to r``\vec{r}`` and acceleration
    is directed towards the origin
    (4) Velocity is perpendicular to r``\vec{r}`` and acceleration
    is directed away from the origin.
    digAnsr:   3
    Ans : 3
    Sol. =  + 

    ˆ ˆr cos t x sin t y
    =   +  
     ˆ ˆv sin t x cos t y
    =   +  = 
     2 2ˆ ˆa cos t x sin t y r
    =
     
    r.v 0 hence 
     
    r v

    a is directed towards the origin.