A woman on a bridge 77.4 m high sees a raft floating at a constant speed on the river below. She drops a stone from rest in an attempt to hit the raft. The stone is released when the raft has 7.07 m more to travel before passing under the bridge. The stone hits the water 4.18 m in front of the raft. Calculate the speed of the raft.

Answer 1

The raft moves 11.25 m during the time it takes for the stone to hit the water. Compute that time (t) and then use it to compute the raft's velocity.

77.4 m = (g/2) t^2 leads to ->

t = 3.97 s

Take it from there

Answer 2

Sorry about the repeat post; computer problems here