$A$ particle of mass $m$ is driven by a machine that delivers a constant power $k$ watts. If the particle starts from rest,the force on the particle at time $t$ is:

  • A
    $\sqrt {\frac{{mk}}{2}} \;{t^{ - \frac{1}{2}}}$
  • B
    $\sqrt {mk} \;{t^{ - \frac{1}{2}}}$
  • C
    $\sqrt {2mk} \;{t^{ - \frac{1}{2}}}$
  • D
    $\frac{1}{2}\sqrt {mk} \;{t^{ - \frac{1}{2}}}$

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