$A$ train engine of mass $m$ starts moving such that its velocity varies as $v = k\sqrt{s}$,where $k$ is a constant and $s$ is the distance covered. What is the total work done by all the forces acting on the engine in the first $t$ seconds?

  • A
    $W = \frac{1}{8} m k^4 t^2$
  • B
    $W = \frac{1}{4} m^2 k^4 t^2$
  • C
    $W = \frac{1}{4} m k^4 t^4$
  • D
    $W = \frac{1}{8} m k^4 t^2$

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