Zeen asks:
A boy jumps from rest, straight down from the top of a cliff. He falls halfway down to the water below in 0.800 s. How much time passes during his entire trip from the top down to the water? Ignore air resistance.
Answer :
let the total height be h
So, for first case
S = h/2
a = g=10 m/s^2
u=0 m/s
t = 0.8 sec
using the relation
h/2 = 0.5 x 10×0.8 ^2
h=6.4 m
In second case (considering the full motion)
S=h=6.4m
t=?
a=g=10m/s^2
u=o m/s
using the relation
6.4 = 0.5 x 10 x t^2
or
t = 2 x 6.4/10 = 1.28 s
here we have to use Newton’s equations of motion.