Answer:
h = 219.96 m
Step-by-step explanation:
Speed of the stone with which it was thrown horizontally, v = 10 m/s
We need to find the height of the cliff if the stone’s trajectory time from the top of the hill to the bottom to be 6.7s.
It means we need to find the distance covered by the stone. As the horizontal speed of the stone is given , it means there is no vertical motion in the stone,u'=0
Using second equation of motion,

Put u'=0 and a=g
So,

So, the height of the cliff is 219.96 m.