Question

Question #f7702

Answer 1

4 sec

Explanation:

Time in free falling `t=8 sec`
after 8 sec the body touches the ground.
Initial velocity is zero.
Initial Velocity `u=0`
Acceleration `a=g`

Using Newton's second equation of Motion
`s=ut+1/2at^2`
first we find total distance `h`

`h=0+1/2(9.8)8^2=313.6 m`
Hence
`h/4=313.6/4=78.4m`

time taken to travel distance 78.4m
`78.4=0+1/2(9.8)t^2`
`9.8t^2=156.8`
`t^2=16`
`t=4 sec`