<PRE><B>Question 1088268</B>
A) -5t^2+45 = -5(2)^2+45 = 25 meters
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B) The ball has to drop 45 meters (the height of the building). 
Gravity: g = 9.8 m/s^2
y: vertical displacement in meters (45 meters)
t = sqrt(2gy)/g
t = sqrt(2gy)/sqrt(g^2) now simplify:
t = sqrt(2y/g)
t = sqrt 2(45)/9.8 = 3.03 seconds
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