Posted by Sierra on .
Two children are playing on a 154mtall bridge. One child drops a rock (initial velocity zero) at
t = 0.
The other waits 1.1 s and then throws a rock downward with an initial speed
v0.
If the two rocks hit the ground at the same time, what is v0

Physics 
Elena,
The time of the first rock fall is
t1=sqrt(2h/g)=sqrt(2•154/9.8) =5.6 s.
The time of the second rock motion øs
t2=t11.1 =5.61.1=4.5 s.
h=vₒt+gt²/2.
vₒ=(h gt²/2)/t= h/tgt/2=154/4.5 9.8•4.5/2 =34.2222.05=12.17 m/s