Question

A stone is dropped from the top of a tower when it has fallen 5m from the top

Answer 1

Let height of tower be 'h'

Time taken for 1st stone to reach ground is =2hg−−−√=2hg

[s=ut+12[s=ut+12gt2gt2;h=12;h=12gt2]gt2]

Time taken for the first stone to be travel 5 m from top =2×5g−−−−√=2×5g

Time taken for 2nd stone to reach ground from a point (h−25)m(h−25)m above the ground is 2(h−25)g−−−−−−−√2(h−25)g

Therefore 2hg−−−√−2×5g−−−−√=2(h−25)g−−−−−−−√2hg−2×5g=2(h−25)g

2h−−√−10−−√=2(h−25)−−−−−−−−√2h−10=2(h−25)

Solving we get h=45m