# Again stones?

I stand the top of a building $$80\text{m}$$ high and my friend Abhay stands at the ground floor of this building. Then, I drop a stone and Abhay throws a stone vertically upward simultaneously. If it is known that Abhay threw the stone at a velocity of $$20\text{m/s}$$, then after how much time (in seconds) would the two stones meet?

Details and assumptions:-

• The acceleration due to gravity($$\text{g}$$) is $$10{\text{m/s}}^2$$.
• The motion of the stones are in a straight vertical line perpendicular to the surface.
• The friction of air is negligible.