Question #f7702

1 Answer
Sep 25, 2017

4 sec

Explanation:

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

Using Newton's second equation of Motion
s=ut+1/2at^2s=ut+12at2
first we find total distance hh

h=0+1/2(9.8)8^2=313.6 mh=0+12(9.8)82=313.6m
Hence
h/4=313.6/4=78.4mh4=313.64=78.4m

time taken to travel distance 78.4m
78.4=0+1/2(9.8)t^278.4=0+12(9.8)t2
9.8t^2=156.89.8t2=156.8
t^2=16t2=16
t=4 sect=4sec