Posted by Yan on .
A ball is dropped from the top of a 49.0 high cliff. At the same time, a carefully aimed stone is thrown straight up from the bottom of the cliff with a speed of 20.0 . The stone and ball collide part way up.

Physics 
Elena,
h1= g•t²/2
h2= v₀•tg•t²/2
h1+h2 =h
g•t²/2 + v₀•tg•t²/2 =49
t= 49/ v₀=49/20 =2.45 s.
h2= v₀•tg•t²/2 =20•2.45 9.8•2.45²/2=
=19.6 m