A block of mass $m$ (initially at rest) is sliding up (in vertical direction) against a rough vertical wall with the help of a force $F$ whose magnitude is constant but direction is changing. $\theta  = {\theta _0}t$  where $t$ is time in sec. At $t$ = $0$ , the force is in vertical upward direction and then as time passes its direction is getting along normal, i.e., $\theta  = \frac{\pi }{2}$ .The value of $F$ so that the block comes to rest when $\theta  = \frac{\pi }{2}$ , is 

818-291

  • A

    $\frac{{mg \times \pi }}{{2{\theta _o}}}$

  • B

    $\frac{{mg \times \pi }}{{2\left( {1 - \mu } \right){\theta _o}}}$

  • C

    $\frac{{mg \times \pi }}{{\left( {1 - \mu } \right)}}$

  • D

    $\frac{{mg \times \pi }}{{2\left( {1 - \mu } \right)}}$

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  • [IIT 2004]