A body falls freely from a height of 125m `(g = 10 m//s^2)` after 2 sec gravity ceases to act Find the time taken by it to reach the ground?

Explanation

Distance covered in 2s under gravity
`s_(1)=1/2 gt^(2)=1/2 (10) (2^(2))=20m`
velocity at the end of 2s, V=gt =(10)2=20m/s.
Now at this instant gravity ceases to act a velocity by here after becomes constant
The remaining distance which is 125-20=105 m is covered by the body with constant velocity of 20 m/s.
Time taken to cover 105 m with constant velocity is given by `t_1=S/V rArr t_(1)=(105)/(20)=5.25s`
Henee total time taken to reach the ground
=2+5.25 =7.25s