Question

A body falls from a height of 120m. . 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

Let distance for the first case be xm
Then for the rest will be (120-x)m
u=0
t₁=2
s=x
v=u+at
v=at
v=10*2=20m/s
v²-u²=2as
400=2*10*s
s=20m
Now final velocity will become the initial velocity
Remaining distance=(120-20)=100m
s=v*t
100=20*t
t=5s
Total time taken=(5+2)s=7s (c)