Originally Posted by **arangu1508** used the formula s = ut + 1/2 at^2
and found the time t; |

Right - you should have at this point that t = sqrt(2s/g)

Originally Posted by **arangu1508** Then I found v = s/t; |

No! this formula applies only if acceleration is 0, but acceleration = g = 10 m/s^2, not 0. You should use v=gt instead, which gives v = sqrt(2gs)

Originally Posted by **arangu1508** Then I found Kinetic Energy using the formula 1/2mv^2;
I did not get the answer. |

If you use the correct formula for 'v' you should get KE= (1/2) mv^2 = (1/2)m (2gs) = mgs.