U=0m/s, t=4sec, a=9m/s^2 (acceleration due to gravity )s=ut+1/2at^2=0×4+1/2×9×4×4=72m, 1/4of72=18m Now, s=18m, u=0m/s, a=9m/s^2 s=ut+1/2at^2=>18=0×t+1/2×9×t^2=>18=1/2×9t^2=>t^2=2×2, hence, t=2
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S = u t + 1/2 a t²

a = g Sin Ф,  where Ф = angle of the inclined plane   
u = 0

Hence, s is directly proportional to t².         If distance is 1/4 th  then time taken will be 1/2.

  So  half of 4 secs  is 2 seconds.
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