$A$ particle of mass $m=1 \ kg$ moves in the $xy$-plane. The force on it at time $t$ is $F(t)=[2 \sin (\alpha t) \hat{i}+3 \cos (\alpha t) \hat{j}] \ N$, where $\alpha=1 \ s^{-1}$. At time $t=0$, the particle is at rest at the origin. Calculate the magnitude of its position vector $r$ (in $m$) and velocity vector $v$ (in $m/s$) at time $t=\frac{\pi}{2} \ s$.

  • A
    $r=\frac{\pi}{2}\sqrt{13}, v=\sqrt{13}$
  • B
    $r=\sqrt{13}, v=\sqrt{9}$
  • C
    $r=\sqrt{3}, v=\sqrt{2}$
  • D
    None of these

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