A rock is dropped from a bridge 320 feet above a river. The pathway that rock takes an be modeled by the equation h = -16t^2 + 320. How long will it take the rock to reach the river? Choose from the correct answer from the following. Show your work
a) 2.5 seconds
b) 3.5 seconds
c) 3.8 seconds
d) 4.5 seconds
To find out how long it will take for the rock to reach the river, we need to set the equation equal to zero and solve for t:
-16t^2 + 320 = 0
-16t^2 = -320
t^2 = 20
t = √20
t ≈ 4.5 seconds
Therefore, the correct answer is:
d) 4.5 seconds