Question

A ball is thrown horizontally from the roof of a building 47.9 m tall and lands 35.4 m from the base. What was the ball's initial speed in m/s?
Hint: Find the horizontal velocity by calculating the time of flight and using the horizontal distance.

Answer 1

find the time it takes for the ball to fall 47.9m

hf=hi-4.9t^2
t= sqrt (47.9/4.9)

velocity=35.4/time

Answer 2

what does the hf and hi stand for?