Question

A body falls from a height of 120 m. After 2 s of fall, if gravity disappears then total time taken to reach the ground is (g = 10 m/s Square)
(a) 9 s (b) 5 s (c) 7 s (d) 10 s

Answer 1

Its 7 sec.....first...
apply....s=ut+1/2at^3....₩here u=0...a=10m/s^2...t=2s...you get...s=20m.....now remaining 100 m...it will fall with teeminal constant velocity....i.e...first find v....using g=(v+u)/t...you get v=20m/s.....now use s=v*t where s=100m...v=20m/s and t=?...calculate...youl get 5s...add it with 2s of before...youll get 7s