The function h(t) = -4.9t^2 + 49t expresses the approximate height, h, in meters, of a ball t seconds after it is launched vertically upward from the ground with an initial velocity of 49 meters per second. After approximately how many seconds will the ball hit the ground?

Question

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Answer 1

It will hit the ground when h = 0
-4.9t^2 + 49t = 0
-4.9t(t - 10) = 0
t = 0 , at the start of the throw,
t = 10 , when it returns to the ground

Answer 2

V = Vo + g*Tr = 0.
49 + (-9.8)Tr = 0,
Tr = 5 s. = Rise time.
Tf = Tr = 5 s. = Fall time.
Tr + Tf = 5 + 5 = 10 s. = Time to reach gnd.