Answer:98.4 m
Explanation:
Given
Descending velocity of balloon(v)=5 m/s
velocity of stone relative to balloon(u)=7 m/s
thus u is the horizontal velocity of stone and v vertical velocity of balloon
time travel by stone to reach ground=4 s
[tex]h=ut+\frac{at^2}{2}[/tex]
where u=initial velocity
here u=5 m/s
t=4 s
a=g
[tex]h=5\times 4+\frac{9.8\times 4^2}{2}=98.4 m[/tex]
horizontal distance traveled in this time
[tex]R=u\times t[/tex]
[tex]R=7\times 4=28 m[/tex]
Thus stone at distance of 28 m from balloon
Also balloon and stone will be at same height at the time when rock hits ground