An object falls freely from rest. It covers the same distance in last second. Which is covered in first 3 seconds, then in .............., it will reach the ground.

An object falls freely from rest. It covers the same distance in last

1.	An object falls freely from rest. It covers the same distance in last second. Which is covered in first 3 seconds, then in .............., it will reach the ground.
Answer» 3s 5S 7s 9s Solution :Suppose last second of free FALL is n. `therefore` Distance covered in `n^(th)` second, `therefore In d _(n) = V _(0) + g/2 (2n -1) , v _(0) =0` `therefore d _(n) = (10)/(2) (2n -1)` `therefore d _(n) = 10 n -5 ""..(i)` and distance covered in first three seconds, `S_(3) = v _(0) t +1/2 g t ^(2) and v_(0) =0, t = 3s, g = 10 MS ^(-2)` `therefore S_(3) =0 xx 3 + 1/2 xx 10 xx 9` `therefore S_(3) = 45M""...(ii)` For given condition `d_(n) = S_(3)` `therefore 10 n - 5=45` `therefore 10n=50` `therefore n = 5s`